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Science MCQ

Atoms and Molecules · Maharashtra Board STD 9 (MSBSHSE - English Medium). 40 questions.

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40 questions · 39 auto-graded MCQ + 1 self-marked written.

MCQ 11 Mark
The anion of an element has:
  • ✓
    More electrons than the normal atom.
  • B
    Less electrons than the normal atom.
  • C
    More protons than the normal atom.
  • D
    Same number of electrons as normal atom.
Answer
Correct option: A.
More electrons than the normal atom.
The anion of an element has more electrons than the normal atom because it is formed by gaining electrons.
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MCQ 21 Mark
In hydrogen peroxide $\ce{(H_2O_2)}$, the proportion of hydrogen and oxygen by mass is:
  • A
    $1 : 8$
  • ✓
    $1 : 16$
  • C
    $8 : 1$
  • D
    $16 : 1$
Answer
Correct option: B.
$1 : 16$
In hydrogen peroxide, the ratio of hydrogen to oxygen is $1 : 16$ by mass.
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MCQ 31 Mark
The element having atomicity ‘four’ is most likely to be:
  • A
    Argon.
  • B
    Fluorine.
  • ✓
    Phosphorus.
  • D
    Francium.
Answer
Correct option: C.
Phosphorus.
Phosphorus has an atomicity of $4.$
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MCQ 41 Mark
The Latin language name of an element is natrium. The English name of this element is:
  • ✓
    Sodium.
  • B
    Potassium.
  • C
    Magnesium.
  • D
    Sulphur.
Answer
Correct option: A.
Sodium.
The English name of the element natrium is Sodium$(Na).$
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MCQ 51 Mark
The atoms of which of the following pair of elements are most likely to exist in free state?
  • A
    Hydrogen and helium.
  • B
    Argon and carbon.
  • C
    Neon and nitrogen.
  • ✓
    Helium and neon.
Answer
Correct option: D.
Helium and neon.
Atoms of helium and neon exist in a free state because they are inert gases and chemically inactive.
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MCQ 61 Mark
The law of constant proportions was given by:
  • ✓
    Proust.
  • B
    Lavoisier.
  • C
    Dalton.
  • D
    Berzelius.
Answer
Correct option: A.
Proust.
The law of constant proportion was proposed by Joseph Proust.
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MCQ 71 Mark
An element which can exhibit valencies of $2, 4$ and $6$ can be:
  • A
    Copper.
  • B
    Iron.
  • C
    Mercury.
  • ✓
    Sulphur.
Answer
Correct option: D.
Sulphur.
Sulphur exhibits the valencies of $2, 4$ and $6.$
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MCQ 81 Mark
If $1.4\ g$ of calcium oxide is formed by the complete decomposition of calcium carbonate, then the amount of calcium carbonate taken and the amount of carbon dioxide formed will be respectively:
  • A
    $2.2\ g$ and $1.1\ g$
  • B
    $1.1\ g$ and $2.5\ g$
  • ✓
    $2.5\ g$ and $1.1\ g$
  • D
    $5.0\ g$ and $1.1\ g$
Answer
Correct option: C.
$2.5\ g$ and $1.1\ g$
Molecular mass of $\ce{CaCO_3}$: $40 + 12 + (16 \times 3) = 100\ g$
Molecular mass of $\ce{CaO}$: $40 + 16 = 56\ g$
Molecular mass of $\ce{CO_2}$​​​​​​​: $12 + (16 \times 2) = 44\ g$
Reaction for the decomposition of calcium carbonate:
$\text{CaCO}_3\xrightarrow{\ \ \ \ \ \ \ \ \ \ \ \ \ }\text{CaO}\ +\ \text{CO}_2\\ \ \ 100\text{g} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 56\text{g}\ \ \ \ \ \ \ \ 44\text{g}\\\ \ \ \ \text{X}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1.4\text{g}\ \ \ \ \ \ \ \ \ \text{Y}$
$56\ g$ of $\ce{CaO}$ is obtained when $100\ g$ of $\ce{CaCO_3}$ is burnt.
Therefore, to get $1.4\ g$ of $\ce{CaO}$, the amount of $\ce{CaCO_3}$​​​​​​​ to be burnt will be $\frac{100\ \times\ 1.4}{56}=2.5\text{g}$
For $\ce{CO_2}$​​​​​​​,
$100\ g$ of $\ce{CaCO_3​​​​​​​}$​​​​​​​ yields $44\ g$ of $\ce{CO_2}$​​​​​​​
Therefore, $2.5\ g$ of $\ce{CaCO_3​​​​​​​}$​​​​​​​ will yield $\frac{44\ \times\ 2.5}{100}=1.1\text{g}$
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MCQ 91 Mark
One $nm$ is equal to:
  • A
    $10^{-9}\ mm.$
  • ✓
    $10^{-7}\ cm.$
  • C
    $10^{-9}\ cm.$
  • D
    $10^{-6}\ m.$
Answer
Correct option: B.
$10^{-7}\ cm.$
One nanometre is equal to $10^{-7}$ centimetre.
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MCQ 101 Mark
Two elements $X$ and $Y$ have valencies of $5$ and $3$, and $3$ and $2$, respectively. The elements $X$ and $Y$ are most likely to be respectively:
  • A
    Copper and sulphur.
  • B
    Sulphur and iron.
  • C
    Phosphorus and nitrogen.
  • ✓
    Nitrogen and iron.
Answer
Correct option: D.
Nitrogen and iron.
Elements $X$ and $Y,$ most likely, are nitrogen and iron.
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MCQ 111 Mark
In water, the proportion of oxygen and hydrogen by mass is:
  • A
    $1 : 4$
  • B
    $1 : 8$
  • C
    $4 : 1$
  • ✓
    $8 : 1$
Answer
Correct option: D.
$8 : 1$
In water, the ratio of oxygen to hydrogen is $8 : 1$ by mass.
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MCQ 121 Mark
The atomicities of ozone, sulphur, phosphorus and argon are respectively:
  • A
    $8, 3, 4$ and $1$
  • B
    $1, 3, 4$ and $8$
  • C
    $4, 1, 8$ and $3$
  • ✓
    $3, 8, 4$ and $1$
Answer
Correct option: D.
$3, 8, 4$ and $1$
The atomicity of ozone$(O_3)$ is $3$, sulphur $(S)- 8$, phosphorus $(P)- 4$, Argon $($noble gas, $Ar)- 1$.
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MCQ 131 Mark
Which of the following represents a correct chemical formula?
  • A
    $\ce{CaCl}$
  • ✓
    $\ce{Na_3N}$
  • C
    $\ce{NaSO_4}$
  • D
    $\ce{NaS}$
Answer
Correct option: B.
$\ce{Na_3N}$
The correct chemical formula among the listed chemicals is of $\ce{Na_3N.}$
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MCQ 141 Mark
If $12$ gram of carbon has $x$ atoms, then the number of atoms in $12$ grams of magnesium will be:
  • A
    $x$
  • B
    $2x$
  • ✓
    $\frac{\text{x}}{2}$
  • D
    $1.5x$
Answer
Correct option: C.
$\frac{\text{x}}{2}$
The number of atoms in $12g$ of magnesium will be $\frac{\text{x}}{2}$
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MCQ 151 Mark
The number of electrons in an ion $Y^{2+}$ is $10$. The atomic number of element $Y$ is most likely to be:
  • A
    $8$
  • ✓
    $12$
  • C
    $10$
  • D
    $14$
Answer
Correct option: B.
$12$
The atomic number of element $Y$ would be $12$.
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MCQ 161 Mark
The law of constant phosphorus, sulphur and krypton, the elements having the lowest and highest atomicities are respectively:
  • A
    Sulphur and krypton.
  • B
    Krypton and ozone.
  • C
    Phosphorus and sulphur.
  • ✓
    Krypton and sulphur.
Answer
Correct option: D.
Krypton and sulphur.
Out of ozone, phosphorus, sulphur and krypton, krypton has the lowest atomicity and sulphur the highest .
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MCQ 171 Mark
Which of the following correctly represents $360g$ water?
$i.\ 2$ moles of $\ce{H_2O}$.
$ii.\ 20$ moles of water.
$iii.\ 6.022 \times 10^{23}$ molecules of water.
$iv.\ 1.2044 \times 10^{25}$ molecules of water.
  • A
    $(i)$
  • B
    $(i)$ and $(iv)$
  • C
    $(ii)$ and $(iii)$
  • ✓
    $(ii)$ and $(iv)$
Answer
Correct option: D.
$(ii)$ and $(iv)$
$20$ moles of water and $1.2044 \times 10^{25}$ molecules of water correctly represent $360\ gms$ of water.
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MCQ 181 Mark
An ionic compound will be formed by the combination of one of the following pairs of elements. This pair of elements is:
  • ✓
    Chlorine and calcium.
  • B
    Calcium and sodium.
  • C
    Sulphur and carbon.
  • D
    Chlorine and chlorine.
Answer
Correct option: A.
Chlorine and calcium.
Chlorine and calcium can form an ionic compound $\ce{CaCl_2}.$
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MCQ 191 Mark
A student wants to have $3.011 \times 10^{23}$ atoms each of magnesium and carbon elements. For this purpose, he will have to weigh:
  • A
    $24\ g$ of magnesium and $6\ g$ of carbon.
  • B
    $12\ g$ of carbon and $24\ g$ of magnesium.
  • C
    $20\ g$ of magnesium and $10\ g$ of carbon.
  • ✓
    $12\ g$ of magnesium and $6\ g$ of carbon.
Answer
Correct option: D.
$12\ g$ of magnesium and $6\ g$ of carbon.
The student will have to weigh $12\ g$ of Magnesium and $6\ g$ of Carbon.
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MCQ 201 Mark
The scientist who proposed the first letter $($or first letter and another letter$)$ of the Latin or English name of an element as its symbol, was:
  • A
    Dalton.
  • B
    Proust.
  • C
    Lavoisier.
  • ✓
    Berzelius.
Answer
Correct option: D.
Berzelius.
Berzelius proposed the first letter $($or first letter and another letter$)$ of the Latin or English name of any element as its symbol.
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MCQ 211 Mark
The English name of an element is potassium, its Latin name will be:
  • A
    Plumbum.
  • B
    Cuprum.
  • ✓
    Kalium.
  • D
    Natrium.
Answer
Correct option: C.
Kalium.
The Latin name of the element potassium is kalium.
Hence, the symbol for potassium is $K.$
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Question 221 Mark
The atomic number of an element $X$ is $13$. What will be the number of electrons in its ion $X^{3+}$^?
Answer
$10$
Explanation:
If the atomic number of $X$ is $13$, the number of electrons in its $X^{3+}$ ion would be $13 - 3 = 10.$
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MCQ 231 Mark
Which of the following pair of elements represents a mole ratio of $1 : 1?$
  • A
    $10g$ of calcium and $12g$ of magnesium.
  • ✓
    $12g$ of magnesium and $6g$ of carbon.
  • C
    $12g$ of carbon and $20g$ of calcium.
  • D
    $20g$ of sodium and $20g$ of calcium.
Answer
Correct option: B.
$12g$ of magnesium and $6g$ of carbon.
$12g$ of magnesium and $6g$ of carbon will have a mole ratio of $1 : 1$
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MCQ 241 Mark
The atomic theory of matter was proposed by:
  • A
    John Kennedy.
  • B
    Lavoisier.
  • C
    Proust.
  • ✓
    John Dalton.
Answer
Correct option: D.
John Dalton.
The atomic theory of matter was proposed by John Dalton.
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MCQ 251 Mark
If $32g$ of sulphur has $x$ atoms, then the number of atoms in $32g$ of oxygen will be:
  • A
    $\frac{\text{x}}{2}$
  • ✓
    $2x$
  • C
    $x$
  • D
    $4x$
Answer
Correct option: B.
$2x$
The number of oxygen atoms in $32g$ of oxygen will be $2x.$
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MCQ 261 Mark
If the number of electrons in an ion $Z^{3-}$ is $10$, the atomic number of element $Z$ will be:
  • ✓
    $7$
  • B
    $5$
  • C
    $10$
  • D
    $8$
Answer
Correct option: A.
$7$
If the number of electrons in an ion $Z^{3-}$ is $10$, the atomic number of element $Z$ will be $7$ because the ion is formed by gaining three electrons.
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MCQ 271 Mark
The formula of the sulphate of an element $X$ is $\ce{X_2(SO_4)_3}.$ The formula of nitride of element $X$ will be:
  • A
    $\ce{X_2N}$
  • B
    $\ce{XN_2}$
  • ✓
    $\ce{XN}$
  • D
    $\ce{X_2N_3}$
Answer
Correct option: C.
$\ce{XN}$
Formula of nitride of the element $X$ will be $\ce{XN.}$
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MCQ 281 Mark
The ratio of moles of atoms in $12g$ of magnesium and $16g$ of sulphur will be:
  • A
    $3 : 4$
  • B
    $4 : 3$
  • ✓
    $1 : 1$
  • D
    $1 : 2$
Answer
Correct option: C.
$1 : 1$
The ratio of moles of atoms in $12g$ of Magnesium and $16g$ of Sulphur will be $1 : 1$
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MCQ 291 Mark
A particle $P$ has $18$ electrons, $20$ neutrons and $19$ protons. This particle must be:
  • A
    A molecule.
  • B
    A binary compound.
  • C
    An anion.
  • ✓
    A cation.
Answer
Correct option: D.
A cation.
Particle $P$ must be a cation.
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MCQ 301 Mark
Molecular compounds are usually formed by the combination between:
  • A
    A metal and a non$-$metal.
  • ✓
    Two different non$-$metals.
  • C
    Two different metals.
  • D
    Any two gaseous elements.
Answer
Correct option: B.
Two different non$-$metals.
Molecular compounds are formed by the combination of two different non$-$metals.
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MCQ 311 Mark
The law of conservation of mass was given by:
  • A
    Dalton.
  • B
    Proust.
  • ✓
    Lavoisier.
  • D
    Berzelius.
Answer
Correct option: C.
Lavoisier.
The law of conservation of mass was given by Lavoisier.
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MCQ 321 Mark
The atomic number of an element $E$ is $16$. The number of electrons in ion $E^{2-}$ will be:
  • A
    $16$
  • ✓
    $18$
  • C
    $15$
  • D
    $14$
Answer
Correct option: B.
$18$
Element with an atomic number $16$ will have $18$ electrons in its $E^{2-}$ ion because anions are formed by gaining electrons.
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MCQ 331 Mark
Which of the following elements has the same molecular mass as its atomic mass?
  • A
    Nitrogen.
  • ✓
    Neon.
  • C
    Oxygen.
  • D
    Chlorine.
Answer
Correct option: B.
Neon.
Neon’s molecular mass is equivalent to its atomic mass.
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MCQ 341 Mark
The formula of a compound is $X_3Y$. The valencies of elements $X$ and $Y$ will be respectively:
  • ✓
    $1$ and $3$
  • B
    $3$ and $1$
  • C
    $2$ and $3$
  • D
    $3$ and $2$
Answer
Correct option: A.
$1$ and $3$
Valencies of element $X$ and $Y$ will be $1$ and $3$, respectively.
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MCQ 351 Mark
The symbols of the elements cobalt, aluminium, helium and sodium respectively written by a student are as follows. Which symbol is the correct one?
  • A
    $CO$
  • B
    $AL$
  • ✓
    $He$
  • D
    $So$
Answer
Correct option: C.
$He$
The correct symbols of cobalt, aluminium, and sodium are $Co, Al$ and $Na$ respectively.
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MCQ 361 Mark
One of the following elements has an atomicity of ‘one’. This element is:
  • ✓
    Helium.
  • B
    Hydrogen.
  • C
    Sulphur.
  • D
    Ozone.
Answer
Correct option: A.
Helium.
The atomicity of Helium$(He)$ is $1.$
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MCQ 371 Mark
The symbol of a metal element which is used in making thermometers is:
  • A
    $Ag$
  • ✓
    $Hg$
  • C
    $Mg$
  • D
    $Sg$
Answer
Correct option: B.
$Hg$
The symbol of the metal used in making thermometers is $Hg($Mercury$).$
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MCQ 381 Mark
Which of the following has the maximum number of atoms?
  • A
    $18\ g$ of $H_2O$
  • B
    $18\ g$ of $O_2$
  • C
    $18\ g$ of $CO_2$
  • ✓
    $18\ g$ of $CH_4$
Answer
Correct option: D.
$18\ g$ of $CH_4$
$18\ g$ of $CH_4$ has maximum number of atoms.
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MCQ 391 Mark
The cation of an element has:
  • A
    The same number of electrons as its neutral atom.
  • B
    More electrons than a neutral atom.
  • C
    Less protons than a neutral atom.
  • ✓
    Less electrons than a neutral atom.
Answer
Correct option: D.
Less electrons than a neutral atom.
The cation of an element has less electrons than a neutral atom.
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MCQ 401 Mark
A particle $X$ has $17$ protons, $18$ neutrons and $18$ electrons. This particle is most likely to be:
  • A
    A cation.
  • ✓
    An anion.
  • C
    A molecule.
  • D
    A compound.
Answer
Correct option: B.
An anion.
$X,$ most likely, is an anion because the number of electrons is more than the number of protons.
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