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Chemistry M.C.Q (1 Marks)

Some Basic Concepts of Chemistry · Uttarakhand Board (UBSE) STD 11 Science (Uttarakhand - English Medium). 175 questions.

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M.C.Q (1 Marks)

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175 questions · auto-graded multiple-choice test.

MCQ 11 Mark
Avogadro's law finds an application in the determination of :
  • A
    Atomicity of gas.
  • ✓
    Molecular weights of gases.
  • C
    Molecular formula of certain gaseous compoun.
  • D
    All the above.
Answer
Correct option: B.
Molecular weights of gases.
Avogadro's law finds an application in the determination of molecular weights of gases.
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MCQ 21 Mark
If $3.01 \times 10^{20}$ molecules are removed from $98 \ \ce{mg}$ of $\ce{H_2SO_4}$, then number of moles of $\ce{H_2SO_4}$ left are:
  • ✓
    $0.5 \times 10^{-3}$ mol.
  • B
    $0.1 \times 10^{-3}$ mol.
  • C
    $9.95 \times 10^{-3}$mol.
  • D
    $1.66 \times 10^{-3}$mol.
Answer
Correct option: A.
$0.5 \times 10^{-3}$ mol.
Number of moles $\ce{H_2SO_4}$ in $98g$ of $\ce{H_2SO_4}$
$=\frac{98\times10^{-3}\text{g}}{98}=10^{-3}\text{moles}$
Number of moles $\ce{H_2SO_4}$ removed
$=\frac{3.01\times10^{20}}{6.02\times10^{23}}=\frac{1}{2}\times10^{-3}$
$=0.5\times10^{-3}\text{mol}$
Number of moles $\ce{H_2SO_4}$ left
$= 1 \times 10 ^{-3} - 0.5 \times 10^{-3} $
$= 0.5 \times 10^{-3}$ moles.
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MCQ 31 Mark
A certain metal sulphide, $\ce{MS_2}$​, is used extensively as a high temperature lubricant. If $\ce{MS_2}$​ is $40.06\%$ by mass of sulphur, metal $M$ has atomic mass :
  • A
    $160$ amu
  • B
    $64$ amu
  • C
    $40$ amu
  • ✓
    $96$ amu
Answer
Correct option: D.
$96$ amu
Molecular weight of $\ce{MS_2​ = 2S + M}$
$\frac{64}{\text{M}+64}=0.4006$
$\therefore\text{M}=96$
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MCQ 41 Mark
A solution is prepared by dissolving $5.64g$ of glucose in $60g$ of water. Calculate the mass percent of glucose.
  • ✓
    $8.59\%$
  • B
    $6.85\%$
  • C
    $9.34\%$
  • D
    $3.59\%$
Answer
Correct option: A.
$8.59\%$
$\text{Mass percent of glucose}=\frac{\text{mass of glucose }}{\text{mass of solutio}}\times100$
$=\frac{5.64}{(5.64+60)}\times100$
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MCQ 51 Mark
In chulhas, gaps are left between the logs :
  • A
    To decrease the ignition temperature of the fuel.
  • ✓
    To allow the air to enter and facilitate fuel burning.
  • C
    To cut off the supply of air.
  • D
    all of these.
Answer
Correct option: B.
To allow the air to enter and facilitate fuel burning.
It is important to keep gaps between the logs in chulhas to allow the air to enter and facilitate fuel burning.
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MCQ 61 Mark
Given that, the abundances of isotopes $^{54}\ce{Fe}, ^{56} F_4 $ and $^{57} \ce{Fe}$ are $5\%, 90\%$ and $5\%$ respectively, the atomic mass of $\ce{Fe}$ is :
  • A
    $55.85$
  • ✓
    $55.95$
  • C
    $55.75$
  • D
    $56.05$
Answer
Correct option: B.
$55.95$
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MCQ 71 Mark
Which of the following expression of concentration of a solution is independent of temperature?
  • A
    Molarity
  • B
    Normality
  • C
    Formality
  • ✓
    Molality
Answer
Correct option: D.
Molality
$\text{Molality}=\frac{\text{number of moles of solute }}{\text{mass of solvent in kilograms }}$
Since mass is unaffected by the change in temperature, hence molality is independent of temperature.
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MCQ 81 Mark
A student performs a titration with different burettes and finds titre values of $25.2\ mL, 25.25\ mL$ and $25.0\ mL.$ The number of significant figures in the average titre value is :
  • A
    $1$
  • B
    $2$
  • ✓
    $3$
  • D
    $4$
Answer
Correct option: C.
$3$
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MCQ 91 Mark
What is the percentage by weight of sulphuric acid if $13g$ of $\ce{H_2SO_4}$ is dissolved to make $78g$ of solution?
  • A
    $13.2\%$
  • B
    $14.28\%$
  • C
    $20\%$
  • ✓
    $16.6\%$
Answer
Correct option: D.
$16.6\%$
Weight of sulphuric acid $= 13g$
Weight of solution $= 78g$
$\therefore\frac{\text{w}}{\text{W}}\%=\frac{13}{78}\times100=16.6\%$
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MCQ 101 Mark
The relative atomic mass of naturally occurring chlorine is not a whole number. What is the reason for this ?
  • ✓
    Chlorine atoms can have different number of neutrons.
  • B
    Naturally occurring chlorine cannot be obtained pure.
  • C
    Chlorine is unstable.
  • D
    The mass of the electrons has been included.
Answer
Correct option: A.
Chlorine atoms can have different number of neutrons.
The relative atomic mass of an element is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance.
Chlorine has two isotopes available in Nature.
One has At.mass $= 35$ which forms roughly $75\%$ of the naturally available Chlorine.
Another has At.mass $= 37$ which forms roughly $25\%$ of the naturally available Chlorine.
So they have fractional atomic mass.
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MCQ 111 Mark
What will be the ratio of $\ce{Cl}^{35}$ and $\text{Cl}^{37}$ respectively in ordinary chlorine if the atomic weight of chlorine is $35.5$
  • A
    $1 : 3$
  • ✓
    $3 : 1$
  • C
    $1 : 2$
  • D
    $2 : 1$
Answer
Correct option: B.
$3 : 1$
Using average molcular mass formula :
$x(35) + (1−x) (37) = 35.5$
$x = 0.75$
$1 − x = 0.25$
$\frac{0.75}{0.25}=3:1$
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MCQ 121 Mark
$800 g$ of a $40\%$ solution by weight was cooled. $100g$ of solute was precipitated. The percentage composition of remaining solution is:
  • ✓
    $31.4\%$
  • B
    $20.0\%$
  • C
    $23.0\%$
  • D
    $24\%$
Answer
Correct option: A.
$31.4\%$
Solutepresentin $800g$ solution $=800\times\frac{40}{100}=320\text{g}$
Soluteprecipitated $= 100g$
Soluteleft $= 220g$
$\therefore$ Totalweightofsolution $= 800 − 100 = 700g$
$700g $ solution has solute $= 220$
$100g$ solution has solute $=\frac{220}{700}\times100=31.43\%$
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MCQ 131 Mark
Who performed the gold foil experiment?
  • ✓
    Thomson
  • B
    Goldstein
  • C
    Chadwick
  • D
    Rutherford
Answer
Correct option: A.
Thomson
Rutherford's Gold foil experiment proved the existence of a small massive centre to atoms, which was later known as the nucleus of an atom.
Ernest Rutherford, Hans Geiger and Ernest Marsden carried out their Gold foil experiment to observe the effect of alpha particles on the matter.
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MCQ 141 Mark
Which law is not applicable for a nuclear reaction where large amount of energy is released?
  • ✓
    Law of conservation of mass
  • B
    Law of definite proportion
  • C
    Law of multiple proportion
  • D
    Avagrado's law
Answer
Correct option: A.
Law of conservation of mass
The law implies that during any chemical reaction, nuclear reaction, or radioactive decay in an isolated system, the total mass of the reactants or starting materials must be equal to the mass of the products. Mass conservation remains correct if energy is not lost but if energy is released in a nuclear reaction, the law of conservation of mass does not hold any good.
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MCQ 151 Mark
India's uranium supply comes mainly from the Jaduguda mines in :
  • A
    Bihar
  • B
    Madhya Pradesh
  • C
    Maharashtra
  • ✓
    None of these
Answer
Correct option: D.
None of these
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MCQ 161 Mark
Mass number is denoted by :
  • ✓
    $D$
  • B
    $S$
  • C
    $A$
  • D
    $Z$
Answer
Correct option: A.
$D$
The mass number $(A)$ is the number of nucleons, which is the total number of protons and neutrons in the nucleus of an atom.
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MCQ 171 Mark
Which of the following reactions is not correct according to the law of conservation of mass.
  • A
    $2{\ce{Mg(s)}}+{O}_2{(g)}\rightarrow2{\ce{Mg}{O(s)}}$
  • ✓
    $\text{C}_3\text{H}_8\text{(g)}=\text{O}_2\text{(g)}\rightarrow\text{CO}_2\text{(g)}=\text{H}_2\text{O}\text{(g)}$
  • C
    $\text{P}_4\text{(s)}=5\text{O}_2\text{(g)}\rightarrow\text{P}_4\text{O}_{10}\text{(s)}$
  • D
    $\text{CH}_4\text{(g)}=2\text{O}_2\text{(g)}\rightarrow\text{CO}_2\text{(g)}+2\text{H}_2\text{O}\text{(g)}$
Answer
Correct option: B.
$\text{C}_3\text{H}_8\text{(g)}=\text{O}_2\text{(g)}\rightarrow\text{CO}_2\text{(g)}=\text{H}_2\text{O}\text{(g)}$
Since the reaction is not balanced, hence, mass of reactants and products are different. It is against the law of conservation of mass.
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MCQ 181 Mark
When an inflated tyre bursts, the air escaping out will :
  • A
    Get heated up
  • ✓
    Be cooled
  • C
    Not undergo any change in its temperature
  • D
    Be liquified
Answer
Correct option: B.
Be cooled
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MCQ 191 Mark
What is the mass of the solvent present in $200g$ of $25\%\ (w/ W) $ calcium hydroxide solution?
  • ✓
    $150g$
  • B
    $125g$
  • C
    $175g$
  • D
    $100g$
Answer
Correct option: A.
$150g$
Given that Mass of solution $= 200g$ and let mass of solute $= x$
Now, mass of the solute can be calculated as follow : $25=\frac{\text{x}}{200}\times100$
Thus, $x =$ mass of solute $= 50g$
Therefore mass of solvent $=$ mass of solution $-$ mass of solute $= 200 - 50 = 150g$
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MCQ 201 Mark
Dalton’s atomic theory was based on :
  • ✓
    Law of chemical combination.
  • B
    Mass theory.
  • C
    Periodic table.
  • D
    None of the above.
Answer
Correct option: A.
Law of chemical combination.
When substances react, they do so by following certain laws. These laws are called the laws of chemical combination. Law of conservation of mass, the law of definite proportions, the law of multiple proportions, Gay lussac's law of gaseous volumes, Avogadro's law. These formed the basis of Dalton's atomic theory of matter.
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MCQ 211 Mark
Which of the following statements is/ are correct regarding significant figures?
  • A
    All non $-$ zero digits are significant.
  • B
    Significant figures are meaningful digits which are known with certainty.
  • C
    Zero between two non $-$ zero digits are significant.
  • ✓
    All of the above.
Answer
Correct option: D.
All of the above.
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MCQ 221 Mark
$1.020g$ of metallic oxide contains $0.540g$ of the metal. If the specific heat of the metal, $M$ is $0.216\ \ce{ cal deg ^{-1} g^{-1}}$. The molecular formula of its oxide is:
  • A
    $\ce{MO}$
  • ✓
    $\ce{M_2O_3}$
  • C
    $\ce{M_2O_4}$
  • D
    $\ce{M_2O}$
Answer
Correct option: B.
$\ce{M_2O_3}$
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MCQ 231 Mark
What will be the molality of the solution containing $18.25g$ of $\text{HCl }$ gas in $500g$ of water?
  • A
    $0.1m$
  • B
    $1M$
  • C
    $0.5m$
  • ✓
    $1m$
Answer
Correct option: D.
$1m$
$\text{Molility}=\frac{\text{No. of moles of solute}}{\text{Mass of solvent in  kg}}$
$\text{no. of moles}=\frac{18.25}{36.5}=0.5$
$\text{Molality}=\frac{0.5}{0.5}=1\text{m}$
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MCQ 241 Mark
Addition of $6.65 \times 10^4$ and $8.95 \times 10^3,$ in terms of scientific notation will be :
  • ✓
    $7.545 \times 10^4$
  • B
    $75.45 \times 10^3$
  • C
    $754.5 \times 10^2$
  • D
    $75.45 \times 10^0$
Answer
Correct option: A.
$7.545 \times 10^4$
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MCQ 251 Mark
$\ce{Na_2SO_3}​⋅\ce{xH_2O}$ has $50\%\ \ce{H_2​O}$ by mass. Hence $, x$ is :
  • A
    $4$
  • B
    $5$
  • C
    $6$
  • ✓
    $7$
Answer
Correct option: D.
$7$
Molecular mass of $\ce{Na_2SO_3}⋅ \ce{x H_2 O = 126 + 18x}$
Hence, $\frac{18\text{x}}{126+18\text{x}}=0.5{\text{(given)}}$
$\therefore\text{x}=7$
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MCQ 261 Mark
The matter is neither created nor destroyed during any physical or chemical change. This statement is of the :
  • A
    Law of constant proportion.
  • ✓
    Law of conservation of mass.
  • C
    Law of reciprocal proportion.
  • D
    Law of multiple proportion.
Answer
Correct option: B.
Law of conservation of mass.
The law of conservation of mass states that "the matter is neither created nor destroyed during any physical or chemical change".
The Law of conservation of Mass states that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass remains constant. The total mass of the universe is constant within measurable limits.
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MCQ 271 Mark
The mass of hydrogen at $\text{STP},$ that is present in a vessel which can hold $4$ grams of oxygen under similar conditions, is :
  • A
    $1gm$
  • B
    $0.5gm$
  • ✓
    $0.25gm$
  • D
    $0.125gm$
Answer
Correct option: C.
$0.25gm$
Equal volumes of different gases at $\text{STP}$ contains an equal number of moles.
$4g$ oxygen corresponds to $\frac{4}{32}=0.125$ mole.
This is also equal to the number of moles of hydrogen. $1$ mole of hydrogen corresponds to $2gm.$
Hence, $0.125$ mole will correspond to $2 \times 0.125 = 0.25gm.$
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MCQ 281 Mark
What is $\%$ composition of a substance?
  • A
    Sum of all the components.
  • B
    $\%$ composition of the sum of two components.
  • ✓
    $\%$ of the total mass of a substance.
  • D
    None of the above.
Answer
Correct option: C.
$\%$ of the total mass of a substance.
The percent composition of a component in a compound is the percent of the total mass of the compound that is due to that component.
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MCQ 291 Mark
A compound was found to contain $5.37\%$ nitrogen. What is the minimum molecular weight of compound ?
  • A
    $26.07$
  • B
    $2.607$
  • ✓
    $260.7$
  • D
    None of these
Answer
Correct option: C.
$260.7$
$5.37g$ of $N$ in $100g$ compound.
$14\text{g}\text{N}=\frac{100\times14}{5.37}=260.7\text{g}\text{ compound}$
Which is the minimum molecular wt as it should have at least one $N.$
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MCQ 301 Mark
The percentage value of nitrogen in urea is about :
  • ✓
    $46$
  • B
    $85$
  • C
    $18$
  • D
    $28$
Answer
Correct option: A.
$46$
The formula of urea is $\ce{NH_2\ CONH_2}$
$\ce{W_N} = 28$
$\ce{W_C}​ = 12$
$\ce{W_O​} = 16$
$\ce{W_H} = 4$
In $60g$ urea, $\ce{W_N​} = 28g$
$100g$ urea, $\ce{W_N}$ is $=\frac{28}{60}\times100=46\%$
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MCQ 311 Mark
$1u= ?$
  • A
    The mass of one atom of the carbon $-12$ isotope
  • B
    $\frac{1}{12}^\text{th}$ the mass of one atom of the carbon $-16$ isotope
  • ✓
    $\frac{1}{12}^\text{th}$ the mass of one atom of the carbon $-12$ isotope
  • D
    The mass of one atom of the carbon $-16$ isotope
Answer
Correct option: C.
$\frac{1}{12}^\text{th}$ the mass of one atom of the carbon $-12$ isotope
$1u = \frac{1}{12}^\text{th}$ the mass of one atom of the carbon $-12$ isotope.
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MCQ 321 Mark
An organic compound containing $C$ and $H$ has $92.3\%$ of carbon, its empirical formula is :
  • ✓
    $\ce{CH}$
  • B
    $\ce{CH_3}$
  • C
    $\ce{CH_2}$
  • D
    $\ce{CH_4}$
Answer
Correct option: A.
$\ce{CH}$
Element $\%$ $\%$ atomic weight Simplest ratio
$C$ $92.3$ $\frac{92.3}{12}=7.69$ $\frac{7.69}{7.69}=1$
$H$ $7.7$ $\frac{7.7}{1}=7.70$ $\frac{7.70}{7.69}=1$
$\therefore$ Empirical formula $= \ce{CH}$
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MCQ 331 Mark
Two students performed the same experiment separately and each one of them recorded two readings of mass which are given below. Correct reading of mass is $3.0g$. On the basis of given data, mark the correct option out of the following statements.
Student
Readings
 
 $(i)$ $(ii)$
$A$ $3.01$ $2.99$
$B$ $3.05$ $2.95$
  • A
    Results of both the students are neither accurate nor precise.
  • ✓
    Results of student $A$ are both precise and accurate.
  • C
    Results of student $B$ are neither precise nor accurate.
  • D
    Rsults of student $B$ are both precise and accurate.
Answer
Correct option: B.
Results of student $A$ are both precise and accurate.
Average of redings of student $\text{A}=\frac{3.01+2.99}{2}=3.00$
Average of readings of student $\text{B}=\frac{3.05+2.95}{2}=3.00$
Correct reding $= 3.0$
For both the students, average value is close to the correct value.
Hence, readings of both are accurate. But readings of student $A$ are also close to each other $($differ only by $0.02)$ and also close to the average value, hence readings of $A$ are also precise.
But readings of $B$ are not close to each other $($differ by $0.1)$ and hence are not precise. Thus, results of student $A$ are both precise and accurate.
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MCQ 341 Mark
Which term describes the mass of $6.023 \times 10^{23}$ representative particles?
  • ✓
    Molar mass.
  • B
    Avogadro's number.
  • C
    Empirical formula.
  • D
    Molecular formula.
Answer
Correct option: A.
Molar mass.
Molar mass of a compound describes the total mass of $6.023 \times 10^{23}$ atoms or particles of the compound.
Ex : Molar mass of $\ce{H_2​ = 2g}$
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MCQ 351 Mark
Photo $-$ electric cell is not used in :
  • A
    Television.
  • ✓
    Photography.
  • C
    Reproduction of sound in cinema.
  • D
    Automatic switching of street lightening circuits.
Answer
Correct option: B.
Photography.
The exposure meter instead of photo electric cell is used in camera to know the correct time of exposure.
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MCQ 361 Mark
Branch of chemistry deals with structure of matter, the energy changes and theories, laws and principles that explain the transfer motion of matter for one form to another is known as :
  • ✓
    Physical chemistry
  • B
    Inorganic chemistry
  • C
    Organic chemistry
  • D
    Analytical chemistry
Answer
Correct option: A.
Physical chemistry
Physical chemistry deals with structure of matter, the energy changes and theories, laws and principles which explains the transfer motion of matter from one form to another.
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MCQ 371 Mark
If $500\ mL$ of a $5M$ solution is diluted to $1500\ mL,$ what will be the molarity of the solution obtained?
  • A
    $1.5M$
  • ✓
    $1.66M$
  • C
    $0.017M$
  • D
    $1.59M$
Answer
Correct option: B.
$1.66M$
If $500\ ml$ of solution is diluted to $1500\ ml$ of solution.
The morality can be calculated by the formula $M_1V_1 = M_2V_2$
Whereas $M_1 = 5M, V_1 = 500, V_2 = 1500, M_2 =?$
Here we have to find $M_2$.
By pitting values in the formula
$5 \times 500 = 1500 \times M_2$
$\text{M}_2=\frac{2500}{1500}$
$= 1.66M$
Hence the morality is $1.66M$
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MCQ 381 Mark
Atomic mass of an element is :
  • A
    Actual mass of one atom of the element
  • ✓
    Average mass of an atom of different atoms of the element
  • C
    Always a whole number
  • D
    None of these
Answer
Correct option: B.
Average mass of an atom of different atoms of the element
Atomic mass is an average mass of different atoms of an element, as most elements have different isotopes. Atomic mass is usually not a whole number. It can be a fraction.
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MCQ 391 Mark
The mass of a sand and powdered mixture along with a beaker is $56g$. If the mass of the dried mixture is $20g,$ find the $\%$ composition of the mixture in $100g\ ? \ ($weight of beaker $= 20g).$
  • A
    $20\%$
  • B
    $36\%$
  • ✓
    $55\%$
  • D
    $60\%$
Answer
Correct option: C.
$55\%$
Mass of beaker $= 20g$
Mass of mixture $+$ beaker $= 56g$
Mass of mixture $= 56 - 20 = 36g$
Mass of washed and dried sand $= 20g$
$100g$ of mixture contains $=\frac{20}{36}\times100=55\%$ of sand.
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MCQ 401 Mark
If $1 L$ of $O_2$​ at $15^\circ C$ and $750\ mm$ pressure contains $N$ molecules, the number of molecules in $2 L$ of $\ce{SO_2}$​ under the same conditions of temperature and pressure will be :
  • A
    $\frac{\text{N}}{2}$
  • B
    $N$
  • ✓
    $2N$
  • D
    $4N$
Answer
Correct option: C.
$2N$
Under similar conditions of temperature and pressure, equal volume of gas contains equal number of molecules.
$\therefore 1L = N$ molecules
$2L = 2 N$ molecules
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MCQ 411 Mark
Mass can neither be created nor destroyed. This is in agreement with which law of chemical combination?
  • ✓
    Law of definite proportion
  • B
    Law of multiple proportion
  • C
    Law of conservation of mass
  • D
    Law of conservation of momentum
Answer
Correct option: A.
Law of definite proportion
The Law of conservation of mass states that when elements and compounds react to form new products, mass cannot be lost or gained.
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MCQ 421 Mark
Which of the following terms are unitless?
  • A
    Molality.
  • B
    Molarity.
  • ✓
    Mole fraction.
  • D
    normality
Answer
Correct option: C.
Mole fraction.
Mole fraction,
$\text{x}_\text{A}=\frac{\text{n}_\text{A}}{\text{n}_\text{A}+\text{n}_\text{B}}=\frac{\text{Mole of component}}{\text{Total number of moles}}\text{(unitless)}$
Mass percentage $\frac{\text{Mass of component}}{\text{Total mass}}\times100\text{(unitless)}$
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MCQ 431 Mark
A hydrocarbon was found to contain $75\%$ by mass of carbon and $25\%$ by mass of hydrogen. What is empirical formula of the compound?
  • A
    $\ce{C_2H_4}$
  • B
    $\ce{C_2H_6}$
  • ✓
    $\ce{CH_4}$
  • D
    $\ce{C_6H_6}$
Answer
Correct option: C.
$\ce{CH_4}$
$\frac{75}{12}:\frac{25}{1}$
$\Rightarrow6.25:25$
$\Rightarrow1:4$
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MCQ 441 Mark
Who is called father of modern chemistry ?
  • ✓
    Antoine Lavoisier.
  • B
    Gilbert Lewis.
  • C
    Gibbs.
  • D
    Otto Hahn.
Answer
Correct option: A.
Antoine Lavoisier.
Antoine Lavoisier is known as the father of modern chemistry.
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MCQ 451 Mark
How many grams of concentrated nitric acid solution should be used to prepare $250\ mL$ of $\ce{2.0M  HNO_3}?$ The concentrated acid is $70\%\ \ce{HNO_3}$.
  • ✓
    $45.0g$ conc. $\ce{HNO_3}$
  • B
    $90.0g$ conc. $\ce{HNO_3}$
  • C
    $70.0g$ conc. $\ce{HNO_3}$
  • D
    $54.0g$ conc. $\ce{HNO_3}$
Answer
Correct option: A.
$45.0g$ conc. $\ce{HNO_3}$
$\because$ Molarity
$=\frac{\text{Weight of HNO}_3}{\text{Molecular mass of HNO}_3\times\text{Volume of solution (in L)}}$
$\therefore$ Weight of $\ce{HNO_3}$
$=$ Molarity $\times$ Molecular mass Volume $($in $L)$
$= 2 \times 63\times\frac{1}{4} = 31.5\text{g}$
It is the weight of $100\%\ \ce{HNO_3}$
But the given acid is $70\%\ \ce{HNO_3}$
$\therefore$ Its weight $= 31.5\times\frac{100}{70}\text{g} = 45\text{g}.$
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MCQ 461 Mark
The laws of chemical combination formed on the basis of :
  • ✓
    Dalton's atomic theory
  • B
    Dalton's mass theory
  • C
    Both $A$ and $B$
  • D
    None of the above
Answer
Correct option: A.
Dalton's atomic theory
Before Dalton, the concept of the atom was not concrete. Dalton explained atoms based on the laws of chemical combinations. When substances react, they do so by following certain laws. These laws are called the laws of chemical combination. These laws formed the basis of Dalton's atomic theory.
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MCQ 471 Mark
What is the atomic mass $(u)$ of chlorine?
  • A
    $34$
  • ✓
    $35.5$
  • C
    $33$
  • D
    $35$
Answer
Correct option: B.
$35.5$
Chlorine is a chemical element with the symbol $\ce{Cl}$ and atomic number $17$. The second $-$ lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them.
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MCQ 481 Mark
$X g$ of $\ce{Ag}$ was dissolved in $\ce{HNO_3}$ and the solution was treated with excess of $\ce{NaCl},$ when $2.87g$ of $\ce{AgCl}$ was precipitated. The value of $x$ is :
  • A
    $1.08g.$
  • ✓
    $2.16g.$
  • C
    $2.70g.$
  • D
    $1.62g.$
Answer
Correct option: B.
$2.16g.$
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MCQ 491 Mark
Which of the following is the best example to demonstrate the law of conservation of mass?
  • ✓
    $12gm$ of carbon combines with $32gm$ of oxygen to form $44gm$ of $\ce{CO}^2$​.
  • B
    When $72gm$ of carbon is heated in a vacuum and no change in its mass takes place.
  • C
    The weight of a piece of platinum is the same before and after heating in air.
  • D
    None of these
Answer
Correct option: A.
$12gm$ of carbon combines with $32gm$ of oxygen to form $44gm$ of $\ce{CO}^2$​.
According to the law of conservation of mass :
The total mass of the reactant $=$ the total mass of the product.
Mass of reactants $= 12 + 32 = 44$ i.e $w(C) + w($oxygen$)$
Mass of products $= 44$ i.e. $w($carbon dioxide$)$
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MCQ 501 Mark
A compound contains $69.5\%$ oxygen, $30.5\%$ nitrogen and its molecular weight is $92$. The formula of compound is :
  • A
    $\ce{N_2O}$
  • B
    $\ce{NO_2}$
  • ✓
    $\ce{N_2O_4}$
  • D
    $\ce{N_2O_5}$
Answer
Correct option: C.
$\ce{N_2O_4}$
Element $\%$ $\%$ at. wt Ratio
$N$ $30.5$ $\frac{30.5}{14}=2.18$ $1$
$O$ $69.5$ $\frac{69.5}{16}=4.34$ $2$
Empirical formula $= \ce{NO_2}$
Empirical formula weight $= 46$
$\text{n} = \frac{92}{46} = 2$
$\Rightarrow $ Molecular formula $= \ce{(NO_2)_2 = N_2O_4}$
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MCQ 511 Mark
When mass is enclosed in a system and no transfer of material and energy is allowed in or out, it's $ ........ $ will never change.
  • A
    Quality
  • ✓
    Quantity
  • C
    Temperature
  • D
    Shape
Answer
Correct option: B.
Quantity
The law of conservation of mass states: Mass can neither be created nor destroyed in a chemical reaction. According to this law mass of an isolated system will remain constant over time. This means when mass is enclosed in a system and no transfer of material and energy is allowed in or out, its quantity will never change.
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MCQ 521 Mark
What will be the molarity of pure water?
  • A
    $18M.$
  • B
    $50.0M.$
  • ✓
    $55.6M.$
  • D
    $100M.$
Answer
Correct option: C.
$55.6M.$
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MCQ 531 Mark
At same temperature and pressure, equal volumes of gases contain the same number of :
  • ✓
    Molecules
  • B
    Electrons
  • C
    Protons
  • D
    Particles
Answer
Correct option: A.
Molecules
Avogadro's hypothesis : All gases containing equal moles if substance occupy the same volume at the same temperature and pressure.
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MCQ 541 Mark
Who proposed atom as an indestructible entity?
  • A
    Rotherford
  • ✓
    Dalton
  • C
    Thomson
  • D
    Pauli
Answer
Correct option: B.
Dalton
Dalton's Atomic Theory All matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties
Compounds are formed by a combination of two or more different kinds of atoms.
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MCQ 551 Mark
Which is the lightest element in the universe?
  • A
    Helium
  • ✓
    Hydrogen
  • C
    Nitrogen
  • D
    Silicon
Answer
Correct option: B.
Hydrogen
Hydrogen is the lightest element in the universe with atomic number $1$ and so, it has the simplest atomic structure.
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MCQ 561 Mark
Gram molar volume for a gas is always considered at $ ........ $ conditions.
  • A
    $\text{NTP}$
  • ✓
    $\text{STP}$
  • C
    variable temperature
  • D
    None of these
Answer
Correct option: B.
$\text{STP}$
Since volume is a dependent variable and it depends on pressure and temperature always so temperature and pressure should be specified when volume of gas is considered.
For this certain standard conditions are taken as $273K$ and $1$ atm pressure.
And at $\text{STP},$ molar volume is $22.4$ litre.
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MCQ 571 Mark
Which law stated that 'matter is neither created nor destroyed'?
  • A
    Law of multiple proportion.
  • B
    Law of conservation of energy.
  • C
    Law of constant composition.
  • ✓
    Law of conservation of mass.
Answer
Correct option: D.
Law of conservation of mass.
The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.
According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants.
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MCQ 581 Mark
Which of the following is used as standard for determination of atomic mass unit?
  • A
    O$^{16}$
  • ✓
    C$^{12}$
  • C
    H$^1$
  • D
    O$^{17}$
Answer
Correct option: B.
C$^{12}$
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MCQ 591 Mark
Chemistry is sometimes called as :
  • A
    Biological Science
  • ✓
    Central Science
  • C
    Biochemistry
  • D
    Both $A$ and $C$
Answer
Correct option: B.
Central Science
Chemistry is sometimes called as Central Science because it bridges other natural sciences, including physics, geology and biology.
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MCQ 601 Mark
Two gases $A$ and $B$ are taken in same volume containers under similar conditions of temperature and pressure. In container $A,$ there are $'2N\ '$ molecules of gas $A$. The number molecules does container $B$ have:
  • A
    $N$
  • B
    $0.5N$
  • ✓
    $2N$
  • D
    $4N$
Answer
Correct option: C.
$2N$
$1.$ According to Avogadro's law, the equal volume of gases under a similar condition of pressure and temperature contain equal no. of molecules.Therefore the number of molecules in container $B$ will also be $2N$.
$2$. As we know, one mole of each gas occupies $22.4-$ litre volume and one mole of gas contains $\ce{N_A}$ molecules at $\text{STP.}$
So at the same temperature and pressure, the equal volume of gas contains equal no of molecules.
Therefore the number of molecules in container $B$ will also be $2N.$
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MCQ 611 Mark
Definition of chemistry is :
  • ✓
    Physical science that studies the composition, structure, properties and change of matter.
  • B
    Biological science that helps to study the basic functioning of nervous system.
  • C
    Science that helps in studying the galaxy.
  • D
    Physical science that studies the biotic and abiotic aspects of environment.
Answer
Correct option: A.
Physical science that studies the composition, structure, properties and change of matter.
Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry deals with such topics as the properties of individual atoms, how atoms form chemical bonds to create chemical compounds, the interactions of substances through intermolecular forces that give matter its general properties, and the interactions between substances through chemical reactions to form different substances.
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MCQ 621 Mark
An organic compound containing $C, H$ and $O$ has $49.3\%$ carbon, $6.84\%$ hydrogen and its vapour density is $73$. Molecular formula of the compound is :
  • A
    $\ce{{C}_3{H}_5{O}_2}$
  • B
    $\ce{{C}_4{H}_{10}{O}_2}$
  • ✓
    $\ce{{C}_6{H}_{10}{O}_4}$
  • D
    $\ce{{C}_3{H}_{10}{O}_2}$
Answer
Correct option: C.
$\ce{{C}_6{H}_{10}{O}_4}$
Element $\%$ $\%$ atomic weight Simplest ratio
$C$ $92.3$ $\frac{49.3}{12}=4.1$ $\frac{4.1}{2.74}=1.5\times2=3$
$H$ $7.7$ $\frac{6.84}{1}=6.84$ $\frac{6.84}{2.74}=2.5\times2=5$
$O$ $43.86$ $\frac{43.86}{16}=2.74$ $\frac{2.74}{2.74}=1\times2=2$
The empirical formula is $\ce{{C}_3{H}_5{O}_2}$.
Empirical formula weight $= 3 × 12 + 5 × 1 + 2 × 16$
$= 36 + 5 + 32 = 73$
Molecular weight of the compound $= 2 × VD = 2 × 73 = 146$
$\text{n}=\frac{\text{mol. wt.}}{\text{empirical fromula wt.}}=\frac{146}{73}=2$
Molecular formula $=$ Empirical formula $× 2$
$= (\ce{{C}_3{H}_5{O}_2}) × 2=\ce{{C}_6{H}_{10}{O}_4}$​​​​​​​
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MCQ 631 Mark
French chemist $ ........ $ laid the foundation to the scientific investigation of matter by describing that substances react by following certain laws.
  • A
    Dalton
  • B
    Rutherford
  • C
    Antony van Leeuwenhoek
  • ✓
    A. Lavoisier
Answer
Correct option: D.
A. Lavoisier
With the development of more precise ideas on elements, compounds and mixtures, scientists began to investigate how and why substances react. French chemist A. Lavoisier laid the foundation to the scientific investigation of matter by describing that substances react by following certain laws. These laws are called the laws of chemical combination. These eventually formed the basis of Dalton's Atomic Theory of Matter.
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MCQ 641 Mark
Which of the following statements about a compound is incorrect?
  • A
    A molecule of a compound has atoms of different elements.
  • B
    A compound cannot be separated into its constituent elements by physical methods of separation.
  • ✓
    A compound retains the physical properties of its constituent elements.
  • D
    The ratio of atoms of different elements in a compound is fixed.
Answer
Correct option: C.
A compound retains the physical properties of its constituent elements.
A compound does not retain the physical or chemical properties of its constituent elements.
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MCQ 651 Mark
If $1\ mL$ of water contains $20$ drops then number of molecules in a drop of water is :
  • A
    $6.023 \times 10^{23}$ molecules.
  • B
    $1.376 \times 10^{26}$ molecules.
  • ✓
    $1.62 \times 10^{21}$ molecules.
  • D
    $4.346 \times 10^{20}$ molecules.
Answer
Correct option: C.
$1.62 \times 10^{21}$ molecules.
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MCQ 661 Mark
16g of oxygen has same number of molecules as in:
  • A
    16g of CO
  • B
    28g of N$_2$
  • C
    18g of N$_2$
  • ✓
    1.0g of H$_2$
Answer
Correct option: D.
1.0g of H$_2$
Explanation: (D) 1.0g of H$_2$
Number of molecules of O$_2$ in 16g of O$_2$
$=\frac{16}{32}\times6.023\times10^{23}$
$0.5\times6.023\times10^{23}$
0.5 moles in present in 14g N$_2$ and 1g H$_2$, hence these samples will also have (0.5 × 6,023 × $10^{23}$) molecules.
Number of molecules of N$_2$
$=\frac{\text{w}}{\text{mol.wt.}}\times 6.023\times10^{23}$
$=\frac{14}{28}\times6.023\times10^{23}$
$=0.5\times6.023\times10^{23}$
Number of molecules of H$_2$ $=\frac{1}{2}\times6.023\times10^{23}$
$=0.5\times6.023\times10^{23}$
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MCQ 671 Mark
During any chemical change, the total mass of the products is equal to the total mass of reactants. This is a statement according to :
  • ✓
    Law of conservation of mass
  • B
    Law of constant composition
  • C
    Law of multiple proportion
  • D
    Law of reciprocal proportion
Answer
Correct option: A.
Law of conservation of mass
According to the law of conservation of mass, the mass of products in a reaction must be equal to the mass of reactants, which can be stated as "mass is neither created nor destroyed during a chemical reaction".
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MCQ 681 Mark
It can be shown using mass spectrometry that the ratio of naturally occurring chlorine $-35$ to its isotope chlorine $-37$ is $3 : 1$. Assuming that no other isotopes existed, what would be the atomic weight of chlorine?
  • ✓
    $35.5$
  • B
    $37.5$
  • C
    $36.6$
  • D
    None of the above
Answer
Correct option: A.
$35.5$
Atomic weight of chlorine $=\frac{3\times35+1\times37}{4}=35.5$
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MCQ 691 Mark
A hydrocarbon was found to contain $85.7\%$ by mass of carbon and $14.3\%$ by mass of hydrogen. Molar mass of hydrocarbon is $56g\ \ce{mol}^{-1}$. The formula for hydrocarbon is
  • A
    $\ce{CH_4}$
  • B
    $\ce{C_2H_4}$
  • ✓
    $\ce{C_4H_8}$
  • D
    $\ce{C_5H_{10}}$
Answer
Correct option: C.
$\ce{C_4H_8}$
$\frac{85.7}{12}:\frac{14.3}{1}$
$\Rightarrow 7.15:14.3$
$\Rightarrow 1:2$
$\ce{CH_2}$ is emprirical formula, $\text{n}=\frac{56}{14}=4$
$​​\text{M.F.}=\text{n}(\text{E.F})=4\times(\text{CH})_2=\text{C}_4\text{H}_8$
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MCQ 701 Mark
When magnesium is burnt in air, the weight of magnesium :
  • ✓
    Increases
  • B
    Decreases
  • C
    Remains same
  • D
    Depends on the atmosphere
Answer
Correct option: A.
Increases
When magnesium is burnt in air, the weight of magnesium increases due to the formation of $\ce{MgO}.$
$\ce{2Mg +O_2 ​\rightarrow 2MgO}$
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MCQ 711 Mark
The volume of $0.5M$ aqueous $\ce{NaOH}$ solution required to neutralize $10\ ml$ of $2M$ aqueous $\ce{HCl}$ solution is :
  • A
    $20\ ml$
  • ✓
    $40\ ml$
  • C
    $80\ ml$
  • D
    $120\ ml$
Answer
Correct option: B.
$40\ ml$
$\ce{NaOH : HCl}$
$\ce{N_1​V_1​ = N_2​V_2 0.5 \times V = 2 \times 10}$
$\ce{V = 40\ mL}$
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MCQ 721 Mark
If the concentration of glucose $\ce{(C_6H_{12}O_6)}$ in blood is $0.9gL^{-1}$, what will be the molarity of glucose in blood?
  • A
    $5M$
  • B
    $50M$
  • ✓
    $0.005M$
  • D
    $0.5M$
Answer
Correct option: C.
$0.005M$
Molar mass of glucose $\ce{(C_6H_{12}O_6)}$
$=12\times6+1\times12+16\times6=180$
$\text{Molarity}=\frac{\text{conc. in gL}^{-1}}{\text{Molar mass}}=\frac{0.90\text{gL}^{-1}}{180\text{g}\ \text{mol}^{-1}}=0.005\text{M}$
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MCQ 731 Mark
Active mass of $6\%$ solution of compound $X$ is $2$. Molecular weight of $X$ would be :
  • A
    $6$
  • ✓
    $30$
  • C
    $60$
  • D
    $90$
Answer
Correct option: B.
$30$
Active mass of $2$ means $2$ moles of $X$ in one litre solution.
$\because 100\ ml$ solution contains $6\ gm$ of $X$
$\therefore 1000\ ml$ solution contains $1006 \times 1000 = 60gm$
$2 $ moles $= 60gm\ X$
$1 $ mole $= 30gm\ X$
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MCQ 741 Mark
A chemical equation is balanced in accordance with the law of :
  • ✓
    Conservation of mass.
  • B
    Multiple proportion.
  • C
    Constant proportion.
  • D
    Reciprocal proportion.
Answer
Correct option: A.
Conservation of mass.
There must be the same number of each element on both side of the chemical equation. It adheres with the conservation of mass.
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MCQ 751 Mark
The mass number of sulfur atom is : $($Given : Atomic number $= 16$ and number of neutrons $= 16)$
  • A
    $18$
  • ✓
    $32$
  • C
    $24$
  • D
    $16$
Answer
Correct option: B.
$32$
Atomic number $=$ number of protons $= 16$
Mass number $=$ Number of protons $+$ number of neutrons
So the mass number of sulfur $= 32$
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MCQ 761 Mark
Uncertainty Principle was given by :
  • ✓
    Heisenberg
  • B
    Thomson
  • C
    Rutherford
  • D
    Bohr
Answer
Correct option: A.
Heisenberg
Heisenberg was the scientist who had given the principle of uncertainty.
According to his principle position and velocity of an object can not be measured at the same time.
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MCQ 771 Mark
The modern atomic mass unit is based on the mass of :
  • ✓
    $C-12$ isotope
  • B
    Hydrogen
  • C
    Oxygen
  • D
    Nitrogen
Answer
Correct option: A.
$C-12$ isotope
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MCQ 781 Mark
In the following reaction, $\ce{MnO_2 +  4HCl \rightarrow MnCl_2 + 2H_2O +Cl_2 2}$ moles of $\ce{MnO_2}$ react with $4$ moles of $\ce{HCl}$ to form $\ce{11.2L Cl_2},$ at $\text{STP}$. Thus, percent yield of $\ce{Cl_2}$ is :
  • A
    $25\%$
  • ✓
    $50\%$
  • C
    $100\%$
  • D
    $75\%$
Answer
Correct option: B.
$50\%$
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MCQ 791 Mark
$25\ cm^3$ of oxalic acid completely neutrelised $0.064g$ of $\ce{NaOH}$. Molarity of oxalic acid solution is :
  • ✓
    $0.064.$
  • B
    $0.045.$
  • C
    $0.015.$
  • D
    $0.032.$
Answer
Correct option: A.
$0.064.$
${\text{COOH}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{ COONa}}$
$\ | \ \ \ \ \ \ \ \ +2\text{NaOH}\xrightarrow{ \ \ \ \ \ \ \ \ \ \ } \ |\ \ \ \ \ \ \ \ \ \ \ \ \ +2\text{H}_2\text{O}$
$\text{COOH} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{COONa}$
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MCQ 801 Mark
Arrange the following in the order of increasing mass $($Atomic mass of $O = 16, Cu = 63$ and $N = 14).$
  1. One atom of oxygen.
  2. One atom of nitrogen.
  3. $1 \times 10-10$ mole of oxygen.
  4. $1 \times 10^{-10}$ mole of copper.
  • ✓
    $\ce{II < I < III < IV}.$
  • B
    $\ce{I < II < III < IV}.$
  • C
    $\ce{III < II < IV < I}.$
  • D
    $\ce{IV < II < III < I}.$
Answer
Correct option: A.
$\ce{II < I < III < IV}.$
  1. Mass of one atom of oxygen
$=\frac{16}{6.022\times10^{23}}=2.66\times10^{-23}\text{g}$
  1. Mass of one atom of nitrogen
$=\frac{14}{6.022\times10^{23}}=2.32\times10^{-23}\text{g}$
  1. Mass of $1 \times 10^{-10}$ mole of oxygen $= 16 \times 10^{-10}$
  2. Mass of $1 \times 10^{-10}$ mole of copper $= 63 \times 10^{-10}$
Hence, masses of atoms in increasing order : $\ce{II < I < III < IV}.$
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MCQ 811 Mark
$4.6 \times 10^{22}$ atoms of an element weight $13.8g$. What is the atomic mass of the element?
  • A
    $290u$
  • ✓
    $180.6u$
  • C
    $34.4u$
  • D
    $104u$
Answer
Correct option: B.
$180.6u$
$1$ mole of any substance contains $6.02 \times 10^{23}$ atoms.
Thus, $4.6 \times 10^{22}$ atoms corresponds to $\frac{4.6\times10^{22}}{6.022\times10^{23}}=0.0764\text{ Moles}$
$0.0764$ moles weighs $13.8g.$
Thus, $1$ mole will weigh$\frac{13.8}{0.0764}=180.6\text{g}$
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MCQ 821 Mark
This is the branch of chemistry deals with chemistry of elements other than carbon and of their compounds :
  • A
    Physical chemistry
  • ✓
    Inorganic chemistry
  • C
    Organic chemistry
  • D
    Analytical chemistry
Answer
Correct option: B.
Inorganic chemistry
Inorganic chemistry deals with chemistry of elements other than carbon and of their compounds. Chemistry of Carbon is called as organic chemistry.
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MCQ 831 Mark
Determine the mass by mass percentage concentration of a $100g$ salt solution which contains $20g$ salt.
  • A
    $30\%$
  • ✓
    $20\%$
  • C
    $80\%$
  • D
    None of these
Answer
Correct option: B.
$20\%$
As we know that,
mass by mass percent $=\frac{\text{ Wt. of salt }}{\text{Total wt. of salt }}\times100$
Given that : $-$
Weight of salt $= 20g$
Total weight of salt $= 100g$
$\therefore $ mass by mass percent $=\frac{20}{100}\times100=20\%$
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MCQ 841 Mark
Which one of the following properties of an element is not variable?
  • A
    Valency
  • ✓
    Atomic weight
  • C
    Equivalent weight
  • D
    All of these
Answer
Correct option: B.
Atomic weight
Atomic weight is specific for a particular element and does not change under any circumstances.
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MCQ 851 Mark
Which scientist proposed the concept of atomic mass?
  • A
    Avogadro
  • B
    Gay Lussac
  • ✓
    Proust
  • D
    Dalton
Answer
Correct option: C.
Proust
The concept of atomic mass was proposed by William Prout. Early atomic mass theory was proposed by the English chemist William Prout in a series of published papers in $1815$ and $1816.$ Known as Prout's Law, Prout suggested that the known elements had atomic weights that were whole number multiples of the atomic mass of hydrogen.
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MCQ 861 Mark
The concentration of a solution or the amount of substance present in its given volume can be expressed in which of the following ways?
  • A
    Mass percent or weight percent $(w/ w\%).$
  • B
    Mole fraction or molarity.
  • C
    Molality.
  • ✓
    All of the above.
Answer
Correct option: D.
All of the above.
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MCQ 871 Mark
A solution is prepared by adding $2g$ of a substance $A$ to $18g$ of water. Calculate the mass percent of the solute.
  • A
    $8\%$
  • B
    $9\%$
  • ✓
    $10\%$
  • D
    $11\%$
Answer
Correct option: C.
$10\%$
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MCQ 881 Mark
Air contains $20\% , 0$ by volume. How much volume of air will be required for combustion of $100cc$ of acetylene?
  • A
    $500cc.$
  • B
    $1064cc.$
  • C
    $212.8cc.$
  • ✓
    $1250cc.$
Answer
Correct option: D.
$1250cc.$
$2\text{C}_2\text{H}_2+5\text{O}_2\xrightarrow{\ \ \ \ \ \ \ \ \ }4\text{CO}_2+2\text{H}_2\text{O}$
$2\text{cc}\ \ \ \ \ \ \ \ \ \ \ 5\text{cc}$
$100\text{cc}\ \ \ \ \ \ \ 250\text{cc}$
Hence, air will be needed $=\frac{100}{20}\times250=1250\text{cc}.$
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MCQ 891 Mark
A mixture of $\ce{24dm}^3$ of hydrogen and $\ce{100dm}^3$ of oxygen was ignited and the reaction mixture was cooled to room temperature and pressure. What will be volume of gases remaining of the end of the reaction?
  • A
    $\ce{24dm}^3$
  • B
    $\ce{76dm}^3$
  • ✓
    $\ce{88dm}^3$
  • D
    $\ce{112dm}^3$
Answer
Correct option: C.
$\ce{88dm}^3$
$\ce{2H_2(g) + O_2(g) \rightarrow 2H_2O(l)}$
$\ce{2dm^3}$ of $\ce{H_2}$ reacts with $\ce{1dm}$ of $\ce{O_2}$
$\ce{24dm^3}$ of $\ce{H_2}$ reacts with $=\frac{1}{2}\times24=12\text{dm}^3\text{of O}_2$
Oxygen unreacted $\ce{= 100 - 12 = 88dm}^3$.
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MCQ 901 Mark
What is the mass percent of carbon in carbon dioxide?
  • A
    $0.034\%$
  • ✓
    $27.27\%$
  • C
    $3.4\%$
  • D
    $28.7\%$
Answer
Correct option: B.
$27.27\%$
Molecular formula of carbon dioxide is $\ce{CO_2}$​.
Molar mass of carbon dioxide is $\ce{12 + 2(16) = 44g mol.}$
Mass percentage of carbon in carbon dioxide is $\frac{12}{44}\times100=27.27\%$
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MCQ 911 Mark
A bivalent metal has an equivalent mass of $32$. The molecular mass of the metal nitrate is :
  • A
    $182$
  • B
    $168$
  • C
    $192$
  • ✓
    $188$
Answer
Correct option: D.
$188$
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MCQ 921 Mark
According to the Avogadro's Law, equal volumes of two different gases, under same conditions of temperature and pressure, contain equal number of :
  • A
    Atoms
  • ✓
    Molecules
  • C
    Electrons
  • D
    Protons
Answer
Correct option: B.
Molecules
Avogadro's Law states that equal volumes of two different gases, under the same conditions of temperature and pressure, contain an equal number of molecules.
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MCQ 931 Mark
Which set of figures will be obtained after rounding upto three significant figures $1.386, 4.334, 2.808\ ?$
  • A
    $1.39, 4.34, 2.809$
  • ✓
    $1.39, 4.33, 2.81$
  • C
    $1.38, 4.34, 2.800$
  • D
    $1.39, 4.34, 2.80$
Answer
Correct option: B.
$1.39, 4.33, 2.81$
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MCQ 941 Mark
An organic compound on analysis was found to contain $10.06\%$ carbon, $0.84\%$ hydrogen and $89.10\%$ chlorine. What will be the empirical formula of the substance?
  • A
    $\ce{CH_2Cl_2}$
  • ✓
    $\ce{CHCl_3}$
  • C
    $\ce{CCl_4}$
  • D
    $\ce{CH_3Cl}$
Answer
Correct option: B.
$\ce{CHCl_3}$
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MCQ 951 Mark
Which statement is linked with the idea that two identical containers filled with different gases will contain the same number of particles?
  • A
    Mosely
  • ✓
    Avagadro
  • C
    Dalton
  • D
    Mendeleev
Answer
Correct option: B.
Avagadro
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MCQ 961 Mark
How many moles are present in $6.023 \times 10^{22}$ molecules of $\ce{CO_2}\ ?$​
  • A
    $0.2$
  • B
    $0.01$
  • ✓
    $0.1$
  • D
    $0.02$
Answer
Correct option: C.
$0.1$
$1$ mole of $\ce{CO_2}$​ contains $1\ NA$​ molecules. $( NA ​= 6.023 \times 10^{23})$
Moles present in given sample are : $6.023 \times 10^{22} \div NA​ = 0.1$
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MCQ 971 Mark
An alkaloid contains $17.28\%$ of nitrogen and its molecular mass is $162.$ The number of nitrogen atoms present in one molecule of alkaloid is :
  • A
    $5$
  • B
    $4$
  • C
    $3$
  • ✓
    $2$
Answer
Correct option: D.
$2$
$100g$ alkaloid contains nitrogen $= 17.28g$
$\therefore 162g$ alkaloid will contain nitrogen $=\frac{17.28 \times 162}{100}=27.9\text{g}\simeq28\text{g}.$
Atomic weight of nitrogen $= 14$
So, number of atoms of nitrogen present in one molecule of alkaloid $=\frac{28}{14}=2.$
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MCQ 981 Mark
Elements $X, Y$ and $Z$ have atomic numbers $5, 9$ and $11$ respectively. Which one forms an anion?
  • A
    $X$
  • ✓
    $Y$
  • C
    $Z$
  • D
    Both $B$ and $C$
Answer
Correct option: B.
$Y$
Atomic number of $X$ is $5$ and electronic configuration is: $2, 3$
Atomic number of $Y$ is $9$ and electronic configuration is: $2, 7$
Atomic number of $Z$ is $12$ and electronic configuration is: $ 2, 8, 1$
$Y$ is one electron short of stable completely filled configuration and thus readily accepts one electron to form an anion.
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MCQ 991 Mark
Law of conservation of mass was put forward by :
  • ✓
    Lavoisier
  • B
    Dalton
  • C
    Priestly
  • D
    Thomson
Answer
Correct option: A.
Lavoisier
The Law of conservation of mass was put forward by Russian scientist Lomonosov in the year $1765.$ Later in $1783, $ French scientist Antoine Lavoisier also stated the same law independently.
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MCQ 1001 Mark
The relative atomic masses of many elements are not whole numbers because :
  • A
    Of different natural abundance of different isotopes
  • B
    Of the concept average atomic masses
  • C
    Of the existence of isotopes
  • ✓
    All of these
Answer
Correct option: D.
All of these
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MCQ 1011 Mark
Which of the following represents largest number of particles.
  • ✓
    Atoms in mole of $\ce{CH_4}$
  • B
    Atoms in $0.5$ mol of $\ce{SO_3}$
  • C
    Atoms in $0.5$ mole of $\ce{CO_2}$
  • D
    Atoms in $1$ mol of $\ce{CO}.$
Answer
Correct option: A.
Atoms in mole of $\ce{CH_4}$
$I$ mole of $\ce{CH_4 } = 5 \times 6.022 \times 10^{23}$,
$0.5$ mol of $\ce{SO_3}= 4 \times 0.5 \times 6.022 \times 10^{23}$,
$0.5$ mole of $\ce{CO_2}= 0.5 \times 3 \times 6.022 \times 10^{23}$,
$I$ mole of $\ce{CO = 2 \times 6.022 \times 10^{23}}$
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MCQ 1021 Mark
One $\text{a.m.u}$ is defined as mass of :
  • A
    $\frac{1}{16}^{\text{th}}$ mass of one oxygen atom
  • B
    $\frac{1}{14}^{\text{th}}$ mass of one atom of nitrogen
  • ✓
    $\frac{1}{12}^{\text{th}}$ mass of one carbon $-12$ atom
  • D
    None of above
Answer
Correct option: C.
$\frac{1}{12}^{\text{th}}$ mass of one carbon $-12$ atom
One $\text{a.m.u}$. is defined as mass of $\frac{1}{12}^\text{th}$ the mass of one carbon $-12$ atom.
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MCQ 1031 Mark
When two molecules of hydrogen react with one molecule of oxygen, the mass of reactants is $36,$ what is the mass of products?
  • A
    $18$
  • ✓
    $36$
  • C
    $9$
  • D
    $32$
Answer
Correct option: B.
$36$
The Law of conservation of mass states that the total mass of reactants is equal to the total mass of products. In any chemical reaction, the total mass of the substance before and after the reaction is the same although its matter undergoes a physical change.
$\ce{2H_2 + O_2​ ⟶ 2H_2​O}$
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MCQ 1041 Mark
Which of the following options is not correct?
  • A
    $8008 = 8.008 \times 10^3$
  • B
    $208 = 3$
  • C
    $5000 = 5.0 \times 10^3$
  • ✓
    $2.0034 = 4$
Answer
Correct option: D.
$2.0034 = 4$
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MCQ 1051 Mark
The empirical formula and molecular mass of a compound are $\ce{CH_2O }$ and $180g$ respectively. What will be the molecular formula of the compound?
  • A
    $\text{C}_9\text{H}_{18}\text{O}_9$
  • B
    $\text{CH}_2\text{O}$
  • ✓
    $\text{C}_6\text{H}_{12}\text{O}_6$
  • D
    $\text{C}_2\text{H}_4\text{O}_2$
Answer
Correct option: C.
$\text{C}_6\text{H}_{12}\text{O}_6$
Empirical formula mass $= 12 + 2 + 16 = 30$
$\text{n}=\frac{\text{Molecular formula mass}}{\text{Empirical formula mass}}$
$=\frac{180}{30}=6$
Molecular formula $=(\text{CH}_2\text{O})_6=\text{C}_6\text{H}_{12}\text{O}_6$
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MCQ 1061 Mark
Which law states that if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of other element, are in the ratio of small whole numbers?
  • A
    Avogadro's law.
  • B
    Law of definite composition.
  • ✓
    Law of multiple proportions.
  • D
    Gay Lussac's law of gaseous volumes.
Answer
Correct option: C.
Law of multiple proportions.
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MCQ 1071 Mark
A measured temperature on Fahrenheit scale is $200^\circ F.$ What will this reading be on Celsius scale?
  • A
    $40^\circ C$
  • B
    $94^\circ C$
  • ✓
    $93.3^\circ C$
  • D
    $30^\circ C$
Answer
Correct option: C.
$93.3^\circ C$
$^\circ\text{F}=\frac{9}{5}(^\circ\text{C})+32$
$200=\frac{9}{5}(^\circ\text{C})+32$
$(^\circ\text{C})=(200-32)\times\frac{5}{9}$
$(^\circ\text{C})=93.3^\circ\text{C}$
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MCQ 1081 Mark
Mass of atom expressed in atomic mass unit is :
  • ✓
    Atomic mass
  • B
    Molecular mass
  • C
    Atomic number
  • D
    None of the above
Answer
Correct option: A.
Atomic mass
The mass of an atom expressed in amu is known as atomic mass. atomic mass unit defined as a unit of mass used to express atomic and molecular weights, equal to one $-$ twelfth of the mass of an atom of carbon $-12.$
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MCQ 1091 Mark
The number of $\ce{Cl}^-$ and $\ce{Ca}^{2+}$ ions in $222g$ of $\ce{CaCl}_2$ is :
  • ✓
    $\ce{4N_A, 2N_A}$
  • B
    $\ce{2N_A, 4N_A}$
  • C
    $\ce{1N_A​, 2N_A}$​
  • D
    $\ce{2N_A, 1N_A}$
Answer
Correct option: A.
$\ce{4N_A, 2N_A}$
$222g$ of $\ce{CaCl_2}$​ is equal to $2$ moles of $\ce{CaCl}_2$​.
Therefore, it has $2$ moles of $\ce{Ca}^{2+}$ and $4$ moles of $\ce{Cl}^-$.
So, no. of atoms of $\ce{Ca}^{2+}$ and $\ce{Cl}^-$ are $\ce{2N_A}$​ and $\ce{4N_A}$ respectively.
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MCQ 1101 Mark
Chemical hypothesis first emerged in Classical Greece by :
  • A
    Einstein
  • B
    Louis Pasteur
  • ✓
    Aristotle
  • D
    Leuweenhock
Answer
Correct option: C.
Aristotle
A basic chemical hypothesis first emerged in Classical Greece with the theory of four elements as propounded definitively by Aristotle stating that the fire, air, earth and water were the fundamental elements.Everything is formed from a combination of two or more of these elements.
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MCQ 1111 Mark
What is the atomic mass $(u)$ of calcium?
  • A
    $10$
  • B
    $20$
  • C
    $30$
  • ✓
    $40$
Answer
Correct option: D.
$40$
Atomic mass $(u)$ of Calcium is $40 u.$
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MCQ 1121 Mark
The weight ratio of roasted ore, coke and limestone fed into the blast furnace in the manufacture of cast iron is :
  • A
    $8 : 1 : 4$
  • B
    $6 : 4 : 1$
  • ✓
    $8 : 4 : 1$
  • D
    $8 : 4 : 3$
Answer
Correct option: C.
$8 : 4 : 1$
The ratio of roasted ore, coke and limestone fed into the blast furnace in the manufacture of cast iron is $8 : 4 : 1.$
This mixture is known as charge.
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MCQ 1131 Mark
The mass of one mole a chloride formed by metal 'X' is 111.0g. Which one could be formula of chloride?
  • A
    XCl
  • ✓
    XCl$_2$
  • C
    XCl$_3$
  • D
    XCl$_4$
Answer
Correct option: B.
XCl$_2$
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MCQ 1141 Mark
The value of $1$ amu is equal to :
  • A
    $1.66 \times 10^{-8} \mathrm{~g}$
  • B
    $1.66 \times 10^{-4} \mathrm{~g}$
  • C
    $1.66 \times 10^{-16} \mathrm{~g}$
  • ✓
    $1.66 \times 10^{-24} \mathrm{~g}$
Answer
Correct option: D.
$1.66 \times 10^{-24} \mathrm{~g}$
One an amu is $\frac{1}{2}$ of the mass of one carbon $-12$ atom.
It is equal to $\frac{1}{\text{N}_\text{A}}$
$\frac{1}{6.022\times10^{23}}=1.66\times10^{-24}\text{g}$
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MCQ 1151 Mark
Insulin contains $3.4\%$ sulphur. The minimum molecular weight of insulin is :
  • ✓
    $941.176$
  • B
    $944$
  • C
    $945.27$
  • D
    None
Answer
Correct option: A.
$941.176$
$3.4g S$ present in $100g$ insulin.
$\therefore 32g S$ is present in $\frac{100}{3.4}\times32=941.176,$ which is equal to the minimum molecular weight of insulin.
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MCQ 1161 Mark
Which law states that the total mass of the reactants is equal to the total mass of the products in a chemical reaction?
  • A
    Law of constant proportions.
  • B
    Law of conservation of energy.
  • ✓
    Law of conservation of mass.
  • D
    Law of multiple proportions.
Answer
Correct option: C.
Law of conservation of mass.
Law of conservation of mass states that in a chemical reaction, the total mass of the product is equal to the total mass of the reactants.
For example
$\ce{CaCO_3 \rightarrow CaO + CO_2}$ The total mass of reactant $\ce{CaCO_3 = 40 + 12 + (16 \times 3)}= 100$
The mass of $\ce{CaO = 40 + 16 = 56}$
Mass of $\ce{CO_2​ = 12 + (16 \times 2) = 44}$
The total mass of products $\ce{CaO + CO_2 = 56 + 44 = 100.}$
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MCQ 1171 Mark
Which of the following property of an element never changes?
  • A
    Valency
  • ✓
    Atomic weight
  • C
    Both $A$ and $B$
  • D
    None of the above
Answer
Correct option: B.
Atomic weight
The atomic weight is a characteristic property of an element and can never vary.
The valency of an element can vary.
For example, when the ion is in $+\ 2$ and $+\ 3 $ oxidation state, its valency is $2$ and $3$ respectively.
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MCQ 1181 Mark
$18.72g$ of a substance $X$ occupies $1.81\ cm^3$. What will be its density measured in correct significant figures?
  • A
    $10.3g/ \ cm^3$
  • ✓
    $10.34g/ \ cm^3$
  • C
    $10.4g/ \ cm^3$
  • D
    $10.3425g/ \ cm^3$
Answer
Correct option: B.
$10.34g/ \ cm^3$
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MCQ 1191 Mark
Which of the following statements is correct about the reaction given below : $\ce{4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(g)}$
  • ✓
    Total mass of iron and oxygen in reactants $=$ total mass of iron and oxygen in product therefore it follows law of conservation of mass.
  • B
    Total mass of reactants $=$ total mass of product; therefore, law of multiple proportions is followed.
  • C
    Amount of $\ce{Fe_2O_3}$ can be increased by taking any one of the reactants $($iron or oxygen$)$ in excess.
  • D
    Amount of $\ce{Fe_2O_3}$ produced will decrease if the amount of any one of the reactants $($iron or oxygen$)$ is taken in excess.
Answer
Correct option: A.
Total mass of iron and oxygen in reactants $=$ total mass of iron and oxygen in product therefore it follows law of conservation of mass.
$\ce{4Fe = 3O_2 \rightarrow > 2 Fe_2O_3}$ follows law of conservation of mass since mass of reactants is equal to mass of products.
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MCQ 1201 Mark
A gas is found to have the formula $\ce{(CO)_x}$. Its vapour density is $70$. The value of $x$ will be :
  • A
    $7$
  • B
    $4$
  • ✓
    $5$
  • D
    $6$
Answer
Correct option: C.
$5$
Vapour density $= 70$
Molecular mass $= 2 \times 70 = 140$
Formula is $\ce{[CO]_x}$
Therefore molecular mass $= (12 +16)_x = 140$
$= x \times 28 = 140 = x = 5.$
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MCQ 1211 Mark
A sample of ammonia has a mass of $51.1g$. How many molecules are in this sample?
  • A
    $1.8 \times 10^{23}$ molecules
  • B
    $3.6 \times 10^{23}$ molecules
  • C
    $9.1 \times 10^{23}$ molecules
  • ✓
    $1.8 \times 10^{24}$ molecules
Answer
Correct option: D.
$1.8 \times 10^{24}$ molecules
given mass of ammonia is $51.1g$
in this number of moles $=\frac{51.1}{17.031}=18$
Now in a mole, there are $\ce{Na}$ molecules, this is known $6.023 \times 10^{23}$
since $1 \text{ mol} = 6.023 \times 10^{23}$
thus,
$18 \text{ mol} = 18\times 6.023 \times 10^{23} = 1.8 \times 10^{24}$
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MCQ 1221 Mark
Sulphuric acid reacts with sodium hydroxide as follows : $\ce{{H}_2{SO}_4+2 {NaOH}} \rightarrow \ce{{Na}_2{SO}_4+2 {H}_2 {O}}$ When $1L$ of $0.1M$ sulphuric acid solution is allowed to react with $1L$ of $0.1M$ sodium hydroxide solution, the amount of sodium sulphate formed and its molarity in the solution obtained is :
  • A
    $\ce{0.1 mol L^{-1}}$
  • ✓
    $\ce{7.10 g}$
  • C
    $\ce{0.25mol L^{-1}}$
  • D
    $\ce{3.55g}$
Answer
Correct option: B.
$\ce{7.10 g}$
Moles of $\ce{{H}_2{SO}_4}$ taken $= 0.1$ moles
Moles of $\ce{NaOH}$ taken $= 0.1$ moles
As $\ce{{H}_2{SO}_4}$ and $\ce{NaOH}$ react in ratio $1 : 2,$ so $0.1$ moles of $\ce{{H}_2{SO}_4}$ reacts with $0.2$ mole of $\ce{NaOH}$ which we don’t have.
$0.1$ mole of $\ce{NaOH}$ reacts with $0.05$ mole of $\ce{{H}_2{SO}_4}$, so $\ce{NaOH}$ is limiting reactant. Product is calculated w.r.t limiting reactant so Number of moles of $\ce{{Na}_2{SO}_4}$ formed will also be equal to $0.05.$
Mass of $\ce{{Na}_2{SO}_4 = 0.05 \times 142 = 7.1 g}$
Molarity of $\ce{{Na}_2{SO}_4} =\frac{\text{Number of moles}}{\text{Volume in litre}}$
$\frac{0.05}{2}=0.025\text{ mol}\ \text{L}^{-1}$
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MCQ 1231 Mark
In the formation of iron sulphide, by heating iron and sulphur, the mass of iron $(II)$ sulphide $ .......... $ when compared with a total mass of iron and sulphur.
  • A
    Increases
  • B
    Decreases
  • ✓
    Remains same
  • D
    None of the above
Answer
Correct option: C.
Remains same
According to the law of conservation of mass, the total mass of reactants is equal to the total mass of products in a chemical reaction.
$\ce{Fe + S \rightarrow FeS}$
The total mass of $\ce{Fe}$ and $S =$ Total mass of iron sulphide
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MCQ 1241 Mark
How many number of molecules and atoms respectively are present in $2.8L$ of a diatomic gas at $\text{STP}\ ?$
  • A
    $6.023 \times 10^{23}, 7.5 \times 10^{23}$
  • B
    $6.023 \times 10^{23}, 15 \times 10^{22}$
  • ✓
    $7.5 \times 10^{22}, 15 \times 10^{22}$
  • D
    $15 \times 10^{22}, 7.5 \times 10^{23}$
Answer
Correct option: C.
$7.5 \times 10^{22}, 15 \times 10^{22}$
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MCQ 1251 Mark
The weight of iron which will be converted into its oxide $\ce{(Fe_3O_4)}$ by the action of $18g$ of steam on it will be $($Atomic weight of $\ce{Fe = 56}).$
  • A
    $168g.$
  • B
    $84g.$
  • ✓
    $42g.$
  • D
    $21g.$
Answer
Correct option: C.
$42g.$
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MCQ 1261 Mark
Who laid the foundation of chemical sciences by experimentally establishing laws of chemical combination along with other scientists?
  • A
    Proust.
  • ✓
    Antoine Lavoisier.
  • C
    Dalton.
  • D
    None of the above.
Answer
Correct option: B.
Antoine Lavoisier.
Lavoisier was the first one who established important laws of chemical combination.
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MCQ 1271 Mark
If the density of a solution is $\ce{3.12g mL^{-1}}$, the mass of $1.5mL$ solution in significant figures is $ ..........$
  • ✓
    $4.7g$
  • B
    $4.680 \times 10^{-3} g.$
  • C
    $4.680g$
  • D
    $4.680g$
Answer
Correct option: A.
$4.7g$
Density of solution $= 3.12g mL^{-1}$
Volume of solution $= 1.5mL$
Mass of solution $=$ Volume $\times $ Density
$\ce{= 1.5 mL} \times \ce{3.12g mL}^{-1}$
$= 4.68g = 4.7g \ ($up to $2$ significant figures$)$
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MCQ 1281 Mark
Which is not one of the laws of chemical combinations?
  • A
    Law of multiple proportion
  • B
    Law of conservation of mass
  • ✓
    Law of conservation of energy
  • D
    Law of definite proportion
Answer
Correct option: C.
Law of conservation of energy
The Law of conservation of energy is not one of the laws of chemical combinations.
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MCQ 1291 Mark
Which of the following is the best thing to do during heavy lighting?
  • A
    Lying on the ground in an open place.
  • B
    Going into the nearest water body.
  • ✓
    Staying indoors away from metallic doors or windows.
  • D
    Standing under a tall tree.
Answer
Correct option: C.
Staying indoors away from metallic doors or windows.
During heavy lightning, the whole cloud fills up with electrical charges. A build up of positive charge builds up on the ground beneath the cloud, attracted to the negative charge in bottom of the cloud. The ground's positive charge concentrates around anything that sticks up $-$ trees, windows, metallic doors and a spark of lightning strikes. So, one should stay away from metallic doors or windows as they are also charged.
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MCQ 1301 Mark
Which of the following statements illustrate the law of multiple proportions?
  • A
    $3.47g$ of $\ce{BaCl_2}$ reacts with $\ce{2.36g{Na}_2{SO}_4}$ to give $\ce{3.88g BaSO_4}$ and $1.95g\ \ce{NaCl}.$
  • B
    Hydrogen sulphide contains $5.89\%$ hydrogen, water contains $11.1\%$ hydrogen and sulphur dioxide contains $50\%$ oxygen.
  • ✓
    An element forms two oxides, $\ce{XO}$ and $\ce{XO_2}$ containing $50\%$ and $60\%$ oxygen respectively. The ratio of masses of oxygen which combines with $1g$ of element $X$ is $2 : 3.$
  • D
    $20\ mL$ ammonia gives $10$ volumes $\ce{N_2}$ and $30$ volumes $\ce{H_2}$ at constant temperature and pressure.
Answer
Correct option: C.
An element forms two oxides, $\ce{XO}$ and $\ce{XO_2}$ containing $50\%$ and $60\%$ oxygen respectively. The ratio of masses of oxygen which combines with $1g$ of element $X$ is $2 : 3.$
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MCQ 1311 Mark
Which law was given by Antoine L. Lavoisier?
  • A
    Laws of multiple proportion
  • ✓
    Law of conservation of mass
  • C
    Both $A$ and $B$
  • D
    None of the above
Answer
Correct option: B.
Law of conservation of mass
Antoine $-$ Laurent Lavoisier established the law of conservation of mass.
It states that "mass can neither be created nor be destroyed in a chemical reaction."
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MCQ 1321 Mark
One of the statements of Dalton’s atomic theory is given below: “Compounds are formed when atoms of different elements combine in a fixed ratio” Which of the following laws is not related to this statement?
  • ✓
    Law of conservation of mass.
  • B
    Law of definite proportions.
  • C
    Law of multiple proportions.
  • D
    Law of conservation of proportions
Answer
Correct option: A.
Law of conservation of mass.
Law of conservation of mass states that matter can neither be created nor destroyer. Avogadro proposed that equal volumes of gases at the same teprerature and pressure should contain equal number of molecules.
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MCQ 1331 Mark
Who is considered as the founding father of chemistry?
  • ✓
    Boyle
  • B
    Aristotle
  • C
    Sir Francis
  • D
    John Mayow
Answer
Correct option: A.
Boyle
Boyle, in particular, is regarded as the founding father of chemistry due to his most important work, the classic chemistry text $-$ "The Sceptical Chymist" $(1661),$ where the differentiation is made between the claims of Alchemy and the empirical scientific discoveries of the new chemistry.He formulated Boyle's law, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions that could be subjected to rigorous experiments.
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MCQ 1341 Mark
The solution of $A$ and $B$ are $0.1$ and $0.2$ molar in a substance. If $100\ \ce{ML}$ of $'A\ '$ are mixed with $25\ mL$ of $B$ and there is no change in volume, then the final molarity of solution is :
  • A
    $0.15M$
  • B
    $0.18M$
  • ✓
    $0.12M$
  • D
    $0.30M$
Answer
Correct option: C.
$0.12M$
$\ce{M_1V_1 + M_2V_2 = M \times V}$
$0.1 \times 100 + 0.2 \times 25 = M \times 125$
$\Rightarrow\text{M}=\frac{10+5}{125}=\frac{15}{125}=0.12$
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MCQ 1351 Mark
Under the same conditions, two gases have the same number of molecules. They must :
  • A
    Be noble gases.
  • ✓
    Have equal volumes.
  • C
    Have a volume of $\ce{22.4 dm}^3$ each.
  • D
    Have an equal number of atoms.
Answer
Correct option: B.
Have equal volumes.
Avogadro's hypothesis : Equal volume of all gases have equal number of molecules $($not atoms$)$ at same temperature and pressures conditions.
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MCQ 1361 Mark
All gases have the same number of moles in the same volume at constant temperature and pressure.
  • A
    Boyle's Law
  • B
    Charles's Law
  • ✓
    Avogadro's Principle
  • D
    Ideal Gas Lawa
Answer
Correct option: C.
Avogadro's Principle
According to the Avogadro's principal, every gas have the same number of moles in the same volume at constant temperature and pressure.
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MCQ 1371 Mark
The weights of two elements which combines with one another are in the ratio of their :
  • ✓
    Atomic weight
  • B
    Molecular weight
  • C
    Quivalent weight
  • D
    None of the above
Answer
Correct option: A.
Atomic weight
According to the law of multiple proportions, when two elements combine to form more than one compound, the weight of one element combined with a fixed weight of the other is in a ratio of small whole numbers.
Hence, the weight of two elements that combine is in the ratio of their atomic weight.
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MCQ 1381 Mark
One mole of any substance contains $6.022 \times 10^{23}$ atoms/ molecules. Number of molecules of $\ce{{H}_2{SO}_4}$ present in $100\ mL$ of $\ce{0.02M  {H}_2{SO}_4}$ solution is $ ..........$
  • ✓
    $12.044 \times 10^{20}$ molecules.
  • B
    $6.022 \times 10^{23}$ molecules.
  • C
    $1 \times 10^{23}$ molecules.
  • D
    $12.044 \times 10^{23}$ molecules.
Answer
Correct option: A.
$12.044 \times 10^{20}$ molecules.
We knew thet $\text{M}=\frac{\text{n}}{\text{v}}$ or $\text{n}=\text{M}\times\text{V}\ (\text{in L})$
$\text{n}=0.02\times0.1=0.002$
No. of molecules $=\text{n}\times6.022\times10^{23}$
$=0.002\times6.022\times10^{23}=12.044\times10^{20}\ \text{molecules}$
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MCQ 1391 Mark
What is the mass of one atom of $C−12$ in grams?
  • ✓
    $\ce{1.992 \times 10^{-23}gm}$
  • B
    $\ce{1.989 \times 10^{-23}gm}$
  • C
    $\ce{1.892 \times 10^{-23}gm}$
  • D
    $\ce{1.965 \times 10^{-23}gm}$
Answer
Correct option: A.
$\ce{1.992 \times 10^{-23}gm}$
Mass of $1$ mole $= \ce{12gm}$
Mass of $\ce{6.022 \times 10^{23} atom = 12gm}$
Mass of $1$ atom $=\frac{12}{6.023\times10^{23}}=1.993\times10^{-23}\text{gm}$
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MCQ 1401 Mark
According to Indian and Greek philosophers at $400\ B.C$. the continuous sub $-$ division of matter would ultimately yield $ .........$
  • ✓
    Atom
  • B
    Electron
  • C
    Proton
  • D
    Neutron
Answer
Correct option: A.
Atom
According to Indian and Greek philosophers at $400\ B.C.,$ the continuous subdivision of matter would ultimately yield atom.
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MCQ 1411 Mark
Which is the $1^{st}$ organic compound synthesized in lab?
  • ✓
    Urea
  • B
    Methanol
  • C
    Ammonia
  • D
    Sulphuric Acid
Answer
Correct option: A.
Urea
It is widely accepted that urea is the first organic compound to be synthesized from inorganic chemicals. In $1828,$ the German chemist Friedrich Wöhler obtained urea artificially by treating silver cyanate with ammonium chloride.
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MCQ 1421 Mark
How many number of aluminium ions are present in $0.051g$ of aluminium oxide?
  • A
    $6.023 \times 10^{23}$ ions.
  • B
    $3$ ions.
  • ✓
    $6.023 \times 10^{20}$ ions.
  • D
    $9$ ions.
Answer
Correct option: C.
$6.023 \times 10^{20}$ ions.
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MCQ 1431 Mark
Which of the following solutions have the same concentration?
  • ✓
    $20g$ of $\ce{NaOH}$ in $200\ mL$ of solution.
  • B
    $0.5$ mol of $\ce{KCl}$ in $100\ mL$ of solution.
  • C
    $40g$ of $\ce{NaOH}$ in $100\ mL$ of solution.
  • D
    $20g$ of $\ce{KOH}$ in $200\ mL$ of solution.
Answer
Correct option: A.
$20g$ of $\ce{NaOH}$ in $200\ mL$ of solution.
$\text{Molarity}=\frac{\text{w}\times\text{1000}}{\text{M}\times\text{V(mL)}}$
  1. $\text{Molarity}=\frac{\text{20}\times\text{1000}}{\text{40}\times\text{200}}=2.5\text{M}$
  2. $\text{Molarity}=\frac{\text{0.5}\times\text{1000}}{\text{200}}=2.5\text{M}$
  3. $\text{Molarity}=\frac{\text{40}\times\text{1000}}{\text{(40}\times\text{100)}}=10\text{M}$
  4. $\text{Molarity}=\frac{\text{20}\times\text{1000}}{\text{(56}\times\text{200)}}=1.785\text{M}$
Thus $(a)$ and $(b)$ have the same molar concentration.
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MCQ 1441 Mark
A solution is prepared by adding $2g$ of substance $A$ to $1g$ of water. The mass percent of the solute is :
  • ✓
    $10$
  • B
    $20$
  • C
    $40$
  • D
    $25$
Answer
Correct option: A.
$10$
The formula for the mass percentage of solute in solution is $=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times100$
Substituting values in the above expression, we get
Mass percentage $=\frac{2}{2+18}\times100=10\%$
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MCQ 1451 Mark
The number of atoms present in one mole of an element is equal to Avogadro number. Which of the following element contains the greatest number of atoms?
  • A
    $\ce{4g He}$
  • B
    $\ce{46g Na}$
  • C
    $\ce{0.40g Ca}$
  • ✓
    $\ce{12g He}$
Answer
Correct option: D.
$\ce{12g He}$
As we new that
Number of atoms $=\text{Mol.}\times\text{N}_\text{A}$
Number of moles $=\frac{\text{wt.}}{\text{Mol. wt.}}$
  1. $4\text{g}\ \text{He}=\frac{4}{4}-1\ \text{mole}$
  2. $46\text{g}\ \text{Na}=\frac{46}{23}=2\ \text{moles}$
  3. $0.40\text{g}\ \text{Ca}=\frac{0.40}{40}=0.01\ \text{mole}$
  4. $12\text{g}\ \text{He}=\frac{12}{4}=3\ \text{moles}$
Hence, $12 \ \ce{g  He}$ of $\ce{He}$ contains the greatest number of atoms.
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MCQ 1461 Mark
Modern atomic mass scale is based on the mass of :
  • A
    $H −1$
  • ✓
    $C −12$
  • C
    $C −14$
  • D
    $C −16$
Answer
Correct option: B.
$C −12$
Modern atomic weight scale is based on $C −12.$
The standard unit for expressing the mass of atom is amu $($atomic mass unit$).$
It is equal to $\frac{1}{12}$ of the mass of an atom of carbon $-12$ equal to $1.6605 \times 10^{-19}g.$
Amu is also called as avogram.
Avogram is a unit of mass and weight equal to one gram divided by the Avogadro's number.
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MCQ 1471 Mark
Which one of the following scientist's proposed the law of conservation of mass?
  • A
    J.J. Thomson
  • ✓
    John Dalton
  • C
    Rutherford
  • D
    Berzelius
Answer
Correct option: B.
John Dalton
The law of conservation of mass is given by John Dalton which states that mass can neither be created nor be destroyed in a chemical reaction.
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MCQ 1481 Mark
A sample of $\ce{{H}_2{SO}_4}$ contains $3.2 \ kg$ of sulphur. The weight $($in $g)$ of hydrogen present in the sample is :
  • A
    $100$
  • ✓
    $200$
  • C
    $50$
  • D
    $150$
Answer
Correct option: B.
$200$
In $\ce{{H}_2{SO}_4}$​ no of moles of hydrogen $= 2\ \times $ no of moles of hydrogen.
Now $3.2\ kg$ of sulphur $= 3200g$ of sulphur $= 100$ moles of sulphur.
So, no fo moles of hydrogen $= 200$ moles.
So weight of the hydrogen $= (1 \times 200) = 200\ gm.$
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MCQ 1491 Mark
Which gas law relates the volume of a gas to the number of molecules of the gas?
  • A
    Gay $-$ Lussac's Law
  • ✓
    Avogadro's Law
  • C
    Boyle's Law
  • D
    Charle's Law
Answer
Correct option: B.
Avogadro's Law
Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules".
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MCQ 1501 Mark
What is mass silicon in $100g$ of sodium silicate, $\ce{{Na}_2{SiO}_3}\ ?$
  • A
    $16.7\%$
  • B
    $23.0\%$
  • C
    $28.0\%$
  • ✓
    $82.0\%$
Answer
Correct option: D.
$82.0\%$
Molar mass of silicon $= \ce{46 + 28 + 48 = 122g mol^{-1}}$
$\%\text{ Si}=\frac{28}{122}\times100=22.95\simeq23\%$
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MCQ 1511 Mark
Which of the following equations is unbalanced?
  • A
    $\ce{4Fe (s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)}.$
  • B
    $\ce{2Mg(s) + O_2(g) \rightarrow 2MgO(s)}.$
  • ✓
    $\ce{P_4(s) + O_2(g) \rightarrow P_2O_{10}(s)}.$
  • D
    $\ce{CH_4(g) + 2O_2(g) \rightarrow CO2(g) + 2H_2O(g)}.$
Answer
Correct option: C.
$\ce{P_4(s) + O_2(g) \rightarrow P_2O_{10}(s)}.$
The unbalanced equation is,
$\ce{P_4(s) + O_2(g) \rightarrow P_4O_{10}(s)}$
It can be balanced as follows:
$\ce{P_4(s) + 5O_2(g) \rightarrow P_4O_{10}(s)}$
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MCQ 1521 Mark
Which law states that in a chemical reaction, the total mass of the products is equal to the total mass of the reactants?
  • A
    Law of constant proportions
  • B
    Law of conservation of energy
  • ✓
    Law of conservation of mass
  • D
    Law of multiple proportions
Answer
Correct option: C.
Law of conservation of mass
The law which states that in a chemical reaction, the total mass of the products is equal to the total mass of the reactants is known as the "Law of conservation of mass".
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MCQ 1531 Mark
Which of the following subatomic particle is lightest?
  • A
    Neutron
  • B
    Alpha particle
  • ✓
    Electron
  • D
    Deuterium
Answer
Correct option: C.
Electron
Alpha particle has highest mass of the given option which is he rest mass of the alpha particle amounts to $6.64424 \times 10^{-27}\ kg.$
Mass of neutron is $1.0086654 \text{ a.m.u.}$
Mass of electrons $= 9.10938291 \times 10^{-31}$ kilograms
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MCQ 1541 Mark
$\%$ composition requires $................ $ of the compound :
  • ✓
    Molar mass
  • B
    Temperature
  • C
    Atmospheric pressure
  • D
    Both $a$ and $b$
Answer
Correct option: A.
Molar mass
The present composition $($by mass$)$ of a compound can be calculated by dividing the mass of each element by the total mass of the compound. i.e. by calculating the molar mass of the compound.
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MCQ 1551 Mark
The result reported in the following multiplication of significant figures $,2.5 \times 1.25 = 3.125$ should be :
  • A
    $3.125$
  • ✓
    $3.1$
  • C
    $3.12$
  • D
    $3.10$
Answer
Correct option: B.
$3.1$
$2.5 \times 1.25 = 3.125$
Since, $2.5$ has two significant figures, the result should not have more than two significant figures thus, it is $3.1.$
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MCQ 1561 Mark
The empirical formula of a compound is $\ce{CH_2}$. One mole of this compound has a mass of $42g$. Its molecular formula is a :
  • ✓
    $\ce{C_3H_6}$
  • B
    $\ce{C_2H_8}$
  • C
    $\ce{CH_2}$
  • D
    $\ce{C_2H_2}$
Answer
Correct option: A.
$\ce{C_3H_6}$
Weight of empirical formula,
$\ce{CH_2 = 12 + (1 \times 2) = 12 + 2 = 14}$
Mass of one mole of the compound $=$ its molecular weight $= 42$
$\text{n}=\frac{\text{Mol. wt.}}{\text{Empirical formula wt.}}=\frac{42}{14}=3$
$\therefore$ Mol. formula $= ($empirical formula$) \times n$
$\ce{= (CH_2) \times 3= C_3H_6}$.
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MCQ 1571 Mark
Law of conservation of mass is also known as :
  • ✓
    Law of indestructibility.
  • B
    Law of mass action.
  • C
    Law of conservation of energy.
  • D
    None of the above.
Answer
Correct option: A.
Law of indestructibility.
Law of Conservation of mass is also known as Law of indestructibility because the mass is conserved and it proves that matter is always conserved and can never be destroyed.
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MCQ 1581 Mark
$1g$ of $\ce{M_2CO_3}$ on treatment with excess $\ce{HCl}$ produces $0.01186$ moles of $\ce{CO_2}$ The molar mass of $\ce{M_2CO_3}$ in $\ce{g mor}^{-1}$ is :
  • A
    $1186$
  • ✓
    $84.3$
  • C
    $118.6$
  • D
    $11.86$
Answer
Correct option: B.
$84.3$
$\ce{M_2CO_3 + 2HCl \rightarrow 2MCl + H_2O + CO_2}$
$0.01186$ mole of $\ce{CO_2}$ is produced from $1g$ of $\ce{M_2CO_3}$
$1$ mole of $\ce{CO_2}$ is produced from $\frac{0}{0.01186}=84.3\text{g}$ of $\ce{{M}_2{CO}_3}$
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MCQ 1591 Mark
The National Physical Laboratory is situated at :
  • A
    Kolkata
  • ✓
    New Delhi
  • C
    Bombay
  • D
    None of these
Answer
Correct option: B.
New Delhi
The $\ce{CSIR}-$ National Physical Laboratory of India is situated in New Delhi.
It maintains standards of $\ce{SI}$ units in India and calibrates the national standards of weights and measures.
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MCQ 1601 Mark
Equal volume of gases contain equal number of moles.State whether the above statement is true or false.
  • ✓
    The statement is True.
  • B
    The statement is False.
  • C
    Neither.
  • D
    Equal volume of gases contain equal number of moles, only when the temperature is increased.
Answer
Correct option: A.
The statement is True.
Avogadro's Law states that at the same temperature and pressure, equal volumes of different gases contain an equal number of particles.
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MCQ 1611 Mark
What is the mass percent of carbon in carbon dioxide?
  • A
    $0.034\%$
  • ✓
    $27.27\%$
  • C
    $3.4\%$
  • D
    $28.7\%$
Answer
Correct option: B.
$27.27\%$
$\text{Mass percent of C in CO}_2=\frac{\text{Molar mass of carbon}\times100}{\text{Molar mass of CO}_2}$
$\therefore\ \%$ of $ \text{C}$ in $\ \text{CO}_2=\frac{12}{44}\times100=27.27\%$
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MCQ 1621 Mark
What is chemistry?
  • A
    Study of substances.
  • B
    Investigation of reactions and properties.
  • C
    Study of reactions to form new substances.
  • ✓
    All of the above.
Answer
Correct option: D.
All of the above.
Chemistry can be defined in many ways as it is study of substance, investigation of reactions and properties and also the study of reactions to form new substance.
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MCQ 1631 Mark
$0.2429g$ sample of potassium is heated in oxygen, $0.440g$ of a crystalline compound is obtained. What is the formula of this compound?
  • A
    $\ce{KO}$
  • B
    $\ce{K_2O}$
  • ✓
    $\ce{KO_2}$
  • D
    $\ce{KO_3}$
Answer
Correct option: C.
$\ce{KO_2}$
Mass of $\ce{K = 0.242g}, $ mass of compound $= 0.440g,$
mass of $O = 0.440 - 0.242 = 0.198g$
Relative molar ratio of $\text{K} = \frac{0.242}{39} = 0.0006$
Relative molar ratio of $\text{O} = \frac{0.198}{16} = 0.012$
Simple ratio of $K = 1$
Simple ratio of $O = 2$
So, the formula is $\ce{KO_2}$.
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MCQ 1641 Mark
One mole of oxygen gas at $\text{STP}$ is equal to $ .........$
  • ✓
    $6.022 \times 10^{23}$ molecules of oxygen.
  • B
    $6.022 \times 10^{23}$ atoms of oxygen.
  • C
    $16g$ of oxygen.
  • D
    $32g$ of oxygen.
Answer
Correct option: A.
$6.022 \times 10^{23}$ molecules of oxygen.
$1$ mole of $\ce{O_2}$ gas at $\ce{STP = 6.022 \times 10^{23}}$ molecules of $\ce{O_2}\ ($Avogadro number$) = 32g$ of $\ce{O_2}$.
Hence, $1$ mole of oxygen gas is equal to molecular weight of oxygen as well as Avogadro number.
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MCQ 1651 Mark
A device for measuring temperatures at a distance is :
  • A
    Gas thermometer
  • B
    Mercury thermometer
  • ✓
    Radiation pyrometer
  • D
    Maximum-minimum thermometer
Answer
Correct option: C.
Radiation pyrometer
Radiation thermometers have the potential to measure an object's temperature at a distance. They can also measure temperatures faster than by other methods.
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MCQ 1661 Mark
The chemical equation is balanced to satisfy one of the following laws in chemical reactions. This law is known as the :
  • ✓
    law of conservation of mass.
  • B
    law of multiple proportions
  • C
    law of chemical equilibrium.
  • D
    None of these.
Answer
Correct option: A.
law of conservation of mass.
Basically, the chemical equations are the symbolic representations of chemical reactions in which the reactants and products are expressed in terms of their respective chemical formulae. These equations satisfy the law that matter can be changed from one form into another but the total amount of mass remains constant. According to the law of conservation of mass, the mass of products in a reaction must be equal to the mass of reactants so the balancing of equations is done to obey this law.
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MCQ 1671 Mark
Which of the following statements is/ are incorrect?
  • ✓
    The weight of a substance can be determined very accurately by using an analytical balance.
  • B
    Volume is denoted in dm units.
  • C
    Density of a substance is its amount present per unit volume.
  • D
    Candela is the luminous intensity, that emits monochromatic radiation of frequency, $\ce{540 \times 10^{12} Hz}$.
Answer
Correct option: A.
The weight of a substance can be determined very accurately by using an analytical balance.
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MCQ 1681 Mark
The average mass of the atom as compared to $\frac{1}{12}^\text{th}$ the mass of one carbon $-12$ atom is known as :
  • A
    Molecular mass.
  • B
    Atomic mass.
  • C
    Relative molecular mass.
  • ✓
    Relative atomic mass.
Answer
Correct option: D.
Relative atomic mass.
The relative atomic mass of the atom is the average mass as compared to $\frac{1}{12}^\text{th}$ of the mass of one carbon $-12$ atom.
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MCQ 1691 Mark
What will be the molality of the solution made by dissolving $10g$ of $\ce{PNaOH}$ in $100g$ of water?
  • ✓
    $2.5m.$
  • B
    $5m.$
  • C
    $10m.$
  • D
    $1.25m.$
Answer
Correct option: A.
$2.5m.$
Molarity $=\frac{\text{Mass of solute}}{\text{mol. mass of solute}}\times\frac{100}{\text{Mass of solvent}}$
$\text{m}=\frac{10}{40}\times\frac{1000}{100}=2.5\text{m}.$
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MCQ 1701 Mark
The average molar mass of air becomes more in presence of which gas if present in air :
  • A
    $\ce{H_2}$
  • B
    $\ce{N_2}$
  • ✓
    $\ce{C_2 H_6}$
  • D
    $\ce{CH_4}$
Answer
Correct option: C.
$\ce{C_2 H_6}$
Molar mass of air is $28.80$ and among given gases, only $\ce{C_2​H_6}$ is heavier than air.
So, it will increase the average molar mass of air.
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MCQ 1711 Mark
Cortisone is a molecular substance containing $21$ atoms of carbon per molecule. The mass percentage of carbon in cortisone is $69.98\%.$ It's molar mass is :
  • A
    $176.5$
  • B
    $252.2$
  • C
    $287.6$
  • ✓
    $360.1$
Answer
Correct option: D.
$360.1$
Let molar mass be $= M$
Mass of $21$ carbon atoms $= 252$
$\%$ of carbon $=\frac{252\times100}{\text{M}}=69.98$
but $\%$ of carbon $= 69.98 \%$
$\therefore M = 360.1$
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MCQ 1721 Mark
Who is given the credit for creation of first nuclear reactor.
  • ✓
    Fermi
  • B
    Niels Bohr
  • C
    Einstein
  • D
    openheimer
Answer
Correct option: A.
Fermi
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MCQ 1731 Mark
$18$ carat gold contains ?
  • A
    $18\%$ gold
  • B
    $4\%$ gold
  • ✓
    $75\%$ gold
  • D
    $60\%$ gold
Answer
Correct option: C.
$75\%$ gold
Caratage is the measurement of purity of gold alloyed with other metals. $24$ carat is pure gold with no other metals. Low caratages contain less gold. $18$ carat gold contain $75\%$ of gold $25\%$ of other metals often, Copper/ Silk.
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MCQ 1741 Mark
Zinc sulphate contains $22.65\%$ zinc and $43.9\%$ water of crystallisation. If the law of constant proportions is true then the weight of zinc required to produce $20g$ of the zinc sulphate crystals will be :
  • A
    $45.3g.$
  • ✓
    $4.53g.$
  • C
    $0.453g.$
  • D
    $453g.$
Answer
Correct option: B.
$4.53g.$
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MCQ 1751 Mark
What will be the molarity of a solution, which contains $5.85g$ of $\ce{NaCl(s)}$ per $500\ mL\ ?$
  • A
    $4\ \ce{mol L^{-1}}$
  • B
    $20\ \ce{mol L^{-1}}$
  • ✓
    $0.2\ \ce{mol L^{-1}}$
  • D
    $2\ \ce{mol L^{-1}}$
Answer
Correct option: C.
$0.2\ \ce{mol L^{-1}}$
$\text{M}=\frac{\text{no. of moles of solute}}{\text{Volime of solution in L}}$
$=\frac{\frac{5.85}{58.5}}{0.5\text{L}}=\frac{0.1}{0.5}=0.2\ \text{mol}\ \text{L}^{-1}$
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