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Chemistry M.C.Q [1M]

Solutions · Bihar Board (BSEB) STD 12 Science (BSEB - English Medium). 151 questions.

Questions · Page 3 of 4

M.C.Q [1M]

MCQ 1011 Mark
A student slowly mixes salt into 25ml of water until no more salt dissolves in it. The student could make more salt dissolve in the solution by:
  • A
    Cooling it
  • B
    Evaporating it
  • C
    Heating it
  • D
    Stirring it
Answer
  1. Heating it

Explanation:

As no more salt is dissolving in the solution, the solution has became saturated solution. The student can dissolve more solution by heating the solution as on heating the saturated solution become supersaturated. After, the solution become supersaturated, no more salt can be dissolved, it will precipitate out.

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MCQ 1021 Mark
Which of the following solutions will have the highest boiling point:
  • A
    1M BaCl2.
  • B
    1M Urea.
  • C
    1M FeCl3.
  • D
    1M NaCl.
Answer
  1. 1M FeCl3.

Explanation:

FeCl3 solution $(\text{T}_\text{b}=\text{T}_\text{b}^0+\Delta\text{T}_\text{b})$ As number of ions produced is maximum in FeCl3 solution. The colligative property $\Delta\text{T}_\text{b}$ will be maximum in case of FeCl3.

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MCQ 1031 Mark
Relative lowering of vapour pressure of a solution is equal to:
  • A
    The mole fraction of solvent
  • B
    The ratio of moles of solute to moles of solvent
  • C
    The mole fraction of solute
  • D
    The ratio of moles of solvent to moles of solute
Answer
  1. The mole fraction of solute

Explanation:

Relative lowering of vapour pressure of a solution is equal to the mole fraction of solute. After adding the solute, the vapour pressure of the solution is found to be lower than that of the pure liquid at a given temperature.

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MCQ 1041 Mark
At a given temperature, osmotic pressure of a concentrated solution of a substance _____________.
  • A
    Is higher than that at a dilute solution.
  • B
    Is lower than that of a dilute solution.
  • C
    Is same as that of a dilute solution.
  • D
    Cannot be compared with osmotic pressure of dilute solution.
Answer
  1. Is higher than that at a dilute solution.

Explanation:

$\pi=\text{CRT}$

Where C is concentration of the solution. So, the higher the concentration of solution at given temperature the higher will be the osmotic pressure.

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MCQ 1051 Mark
The pressure at which liquid and vapour can coexist at equilibrium is called the :
  • A
    Limiting vapour pressure
  • B
    Real vapour pressure
  • C
    Normal vapour pressure
  • D
    Saturated vapour pressure
Answer
  1. Saturated vapour pressure

Explanation:

Ordinary evaporation is a surface phenomenon - some molecules have enough kinetic energy to escape. If the container is closed, then an equilibrium is reached where an equal number of molecules return to the surface. 

The pressure at which this equilibrium where the coexistence of liquid and vapour is achieved is called the saturated vapor pressure.

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MCQ 1061 Mark
12g of a non - volatile solute dissolved in 108g of water produces the relative lowering of the vapour pressure of 0.1. The molecular mass of the solute is:
  • A
    80
  • B
    60
  • C
    20
  • D
    40
Answer
  1. 20

Explanation:

12g of a non - volatile solute dissolved in 108g of water produces the relative lowering of vapour pressure of 0.1.

The molecular mass of the solute is 20.

$\frac{\triangle\text{P}}{\text{P}^0}=0.1$

$\frac{\triangle\text{P}}{\text{P}^0}=\frac{\text{W}_2\text{M}_1}{\text{W}_1\text{M}_2}$

$0.1=\frac{12\text{g}\times18\text{g}/\text{mol}}{108\text{g}\times\text{M}_2}$

$\text{M}_2=20\text{g}/\text{mol}$

Note: W1​ and W2​ are weights of water and solute respectively.

M1​ and M2​ are molecular weights of water and solute respectively.

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MCQ 1071 Mark
The value of Henry’s constant KH is ___________.
  • A
    Greater for gases with higher solubility.
  • B
    Greater for gases with lower solubility.
  • C
    Constant for all gases.
  • D
    Not related to the solubility of gases.
Answer
  1. Greater for gases with lower solubility.

Explanation:

The value of Henry's constant KH is greater for gases with lower solubility because of the mathematical relation.

$\text{P}=\text{K}_\text{H}\times\text{x}$

$\text{K}_\text{H}=\frac{\text{P}}{\text{x}}$

where, KH represents Henry's constant, p is partial pressure of the gas in vapour phase, and x denotes mole fraction of the gas in solution. Thus KH is inversely proportional to mole fraction of gas in solution (representing its solubility).

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MCQ 1081 Mark
Which of the following aqueous solutions should have the highest boiling point?
  • A
    1.0M NaOH
  • B
    1.0M Na2SO4
  • C
    1.0M NH4NO3
  • D
    1.0M KNO3
Answer
  1. 1.0M Na2SO4

Explanation:

In 1.0M Na2SO4 solution vant H off factor, i > 1 and is maximum when compared with the other three given electrolytes. So, the extent of dissociation in case of 1.0M Na2SO4 would be highest yielding maximum no. of ions as compared to the other given electrolytes in their 1.0M solutions.

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MCQ 1091 Mark
For an ideal liquid solution, which of the following is unity?
  • A
    Activity coefficient
  • B
    Fugacity coefficient
  • C
    Fugacity
  • D
    Activity
Answer
  1. Activity coefficient

Explanation:

An activity coefficient is a factor used in thermodynamics to account for deviations from ideal behavior in a mixture of chemical substances.

Hence, for an ideal liquid solution, that deviation is 0, as the mole fraction of other substance is 0.

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MCQ 1101 Mark
The vapour pressure of the solution containing 30g. of non - volatile solute of molecular weight 60 in 360gm of water approximately at 300c is: (vapour pressure of water at 300c = 24mm of Hg)
  • A
    26.8mm
  • B
    25.8mm
  • C
    23.40mm
  • D
    29.4mm
Answer
  1. 23.40mm

Explanation:

Given,

mass of solute 30g

mass of solvent 360g

the molecular mass of solute 60g

the molecular mass of solvent that is water is 18g

The pressure of pure water is 24mmHg

$\frac{\text{p}_0-\text{p}}{\text{P}}$ = moles of solute/ total no.of moles

$\frac{\text{p}_0-\text{p}}{\text{P}}=\frac{\frac{30}{60}}{\frac{30}{60}+\frac{360}{180}}$

$\frac{\text{p}_0-\text{p}}{\text{P}}=\frac{1}{41}$

$\text{P}=23.4\text{mmHg}$

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MCQ 1111 Mark
A zinc metal sample containing zinc chloride as impurity was made to react with an excess of dilute hydrochloric acid at 27°C. Liberated hydrogen gas is collected at 760mm Hg pressure that occupies 780.0cm3 volume. If the vapour pressure of water at 27°C is 14mm Hg, what is the volume of H2​ at STP? The Standard pressure is 760mm Hg (molar volume of gas at standard temperature and pressure, STP = 22.4dm3)
  • A
    746cm3
  • B
    697cm3
  • C
    750cm3
  • D
    300cm3
Answer
  1. 697cm3
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MCQ 1121 Mark
At equilibrium the rate of dissociation of a solid solute in a volatile liquid solvent is:
  • A
    Less than the rate of crystallisation
  • B
    Greater than the rate of crystallisation
  • C
    Equal to the rate of crystallisation
  • D
    Zero
Answer
  1. Equal to the rate of crystallisation
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MCQ 1131 Mark
Which substance would dissolve fastest in water?
  • A
    1g granulated sugar
  • B
    1g powdered sugar
  • C
    1g sugar cube
  • D
    1g piece of crystallized sugar
Answer
  1. 1g granulated sugar

Explanation:

Each Granulated sugar is touched with water so exposed surface is highest from others so its solubility is highest.

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MCQ 1141 Mark
Calculate the vapour pressure of aqueous 0.1m glucose solution at 300K temperature, the vapour pressure of water is 0.03bar at 300K temperature.
  • A
    0.5bar
  • B
    0.29bar
  • C
    0.3bar
  • D
    0.03bar
Answer
  1. 0.03bar
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MCQ 1151 Mark
Two containers, X and Y at 300K and 350K with water vapour pressures 22mm and 40mm respectively a are connected, initially closed with a valve. If the valves opened.
  • A
    The final pressure in each container is 31mm.
  • B
    The final pressure in each container is 40mm.
  • C
    Mass of H2​O(l) in X increases.
  • D
    Mass of H2​O(l) in Y decreases roar.
Answer

  1. The final pressure in each container is 31mm.

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MCQ 1161 Mark
_____________ obeys Raoult’s law in all stages of concentration.
  • A
    Ideal Solution
  • B
    Non - Ideal solution
  • C
    Real Solution
  • D
    None of the mentioned
Answer
  1. Ideal Solution

Explanation:

At all concentration levels, Ideal Solution follows Raoult’s law.

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MCQ 1171 Mark
A mixture of benzene and toluene forms:
  • A
    An ideal solution
  • B
    Non-ideal solution
  • C
    Suspension
  • D
    Emulsion
Answer
  1. An ideal solution

Explanation:

Mixing of benzene and toluene does not involve any kind of decrease or increase in interaction forces in between molecules so they form ideal solution.

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MCQ 1181 Mark
What will be the degree of dissociation of 0.1M Mg(NO3)2 solution if van’t Hoff factor is 2.74?
  • A
    75%
  • B
    87%
  • C
    100%
  • D
    92%
Answer
  1. 87%
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MCQ 1191 Mark
At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is __________.
  • A
    Less than the rate of crystallisation.
  • B
    Greater than the rate of crystallisation.
  • C
    Equal to the rate of crystallisation.
  • D
    Zero.
Answer
  1. Equal to the rate of crystallisation.

Explanation:

This happens as per conditions attained at equilibrium state; i.e. rate of forward reaction (dissolution) = rate of backward reaction (crystallisation)

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MCQ 1201 Mark
The law which indicates the relation’-hip between solubility of a gas in liquid and pressure rs:
  • A
    Raoult’s law
  • B
    Henry’s law
  • C
    Lowering of vapour pressure
  • D
    Van’t Hoff law
Answer
  1. Henry’s law
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MCQ 1211 Mark
Which of the following plot does not represent the behaviour of an ideal binary liquid solution of A and B?
  • A
    Plot of pA​ vs xA​ is linear
  • B
    Plot of pB​ vs xB​ is linear
  • C
    Plot of ptotal​ vs xA​ is linear
  • D
    Plot of ptotal​ vs xB​ is parabola
Answer
  1. Plot of ptotal​ vs xB​ is parabola
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MCQ 1221 Mark
Which of the following options is not a viable option?
  • A
    Brass
  • B
    Bronze
  • C
    Hydrated salts
  • D
    Aerated drinks
Answer
  1. Aerated drinks

Explanation:

A solid solution is a one - or more - solute solid - state solution in a solvent. Solid solutions include brass, bronze, and hydrated salts. Liquid solutions include aerated beverages.

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MCQ 1231 Mark
An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because ___________.
  • A
    It gains water due to osmosis.
  • B
    It loses water due to reverse osmosis.
  • C
    It gains water due to reverse osmosis.
  • D
    It loses water due to osmosis.
Answer
  1. It loses water due to osmosis.

Explanation:

Water starts moving out of mango (lower concentration) to the salt solution (higher concentration) due to osmosis.

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MCQ 1241 Mark
In comparison to a 0.01M solution of glucose, the depression in freezing point of a 0.01M MgCl2 solution is __________.
  • A
    The same.
  • B
    About twice.
  • C
    About three times.
  • D
    About six times.
Answer
  1. About three times.

Explanation:

Depression in freezing point is a colligative property. In case of MgCl2 value of van’t. Hoff factor will be more. No. of ions yielded when a molecule of MgCl2 gets dissociated in its aqueous solution is = 3. Thus one molecule of 0.01M MgCl2 gives out three particles/ ions in solution, thereby increasing the number of particles present in its solution to three times. It is because of this that depression in freezing point of 0.01M MgCl2 will be three times as compared to that of 0.01M - glucose solution, where no dissociation of the molecule takes place.

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MCQ 1251 Mark
Which of the following is a true solution?
  • A
    Sugar-water mixture
  • B
    Copper in silver
  • C
    Milk
  • D
    Mud in water
Answer
  1. Sugar-water mixture
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MCQ 1261 Mark
Which of the following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent?
(a) Nature of solute (b) Temperature (c) Pressure
  • A
    (a) and (c) at constant T.
  • B
    (a) and (b) at constant P.
  • C
    (b) and (c) only.
  • D
    (c) only.
Answer
  1. (a) and (c) at constant T.
  2. (a) and (b) at constant P.

Explanation:

At constant temperature, the solubility of a gaseous solute in liquid depends on nature of solute and pressure. At constant pressure, solubility is dependent upon nature of solute and temperature.

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MCQ 1271 Mark
How much oxygen is dissolved in 100rnL water at 298K if partial pressure of oxygen is 0.5atm and K = 1.4 × 10-3 mol/ L/ atm?
  • A
    22.4mg
  • B
    22.4g
  • C
    2.24g
  • D
    2.24mg
Answer
  1. 2.24mg
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MCQ 1281 Mark
The van't Hoff factor for a solute which does not dissociate or associate in solution is:
  • A
    0
  • B
    2
  • C
    3
  • D
    1
Answer
  1. 1

Explanation:

The Van't Hoff factor for a solute which does not dissociate or associate in solution is 1 as it is non-electrolyte.

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MCQ 1291 Mark
The unit of ebulioscopic constant is ___________.
  • A
    K kg mol-1 or K(molality)-1
  • B
    mol kg K-1 or K-1(molality)
  • C
    kg mol-1 K-1 or K-1(molality)-1
  • D
    K mol kg-1 or K(molality)
Answer
  1. K kg mol-1 or K(molality)-1

Explanation: 

$\text{K}_{\text{b}}=\frac{\Delta\text{T}_{\text{b}}}{\text{m}}=\frac{\text{K}}{\text{mol kg}^{-1}}\text{or K}\text{(molality)}^{-1}$

The unit of ebullioscopic constant is K kg mol-1 or K molality-1

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MCQ 1301 Mark
Which characteristics the weak inter molecular forces of attraction in a liquid?
  • A
    High boiling point
  • B
    High vapour pressure
  • C
    High critical temperature
  • D
    High heat of vapourisation
Answer
  1. High vapour pressure

Explanation:

The stronger the intermolecular forces between the molecules, the harder it is for vaporization to occur since more energy is required to break the bonds holding the molecules together. So, weak intermolecular forces means high vapour pressure.

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MCQ 1311 Mark
Colligative properties depend on __________.
  • A
    The nature of the solute particles dissolved in solution.
  • B
    The number of solute particles in solution.
  • C
    The physical properties of the solute particles dissolved in solution.
  • D
    The nature of solvent particles.
Answer
  1. The number of solute particles in solution.

Explanation:

Colligative properties depend upon the number of solute particles in the solution and independent of its nature.

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MCQ 1321 Mark
For carrying reverse osmosis for desalination of water the material used for making semipermeable membrane is:
  • A
    Potassium nitrate
  • B
    Parchment membrane
  • C
    Cellulose acetate
  • D
    Cell membrane
Answer
  1. Cellulose acetate
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MCQ 1331 Mark
Which of the following statements is false?
  • A
    Units of atmospheric pressure and osmotic pressure are the same.
  • B
    In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.
  • C
    The value of molal depression constant depends on nature of solvent.
  • D
    Relative lowering of vapour pressure, is a dimensionless quantity.
Answer
  1. In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.

Explanation:

In reverse osmosis solvent molecules move through a semipermeable membrane from a region of higher concentration of solute to a region of lower concentration, therefore the given statement at (ii) is false.

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MCQ 1341 Mark
The relative lowering in vapour pressure is proportional to the ratio of number of :
  • A
    Solute molecules to solvent molecules.
  • B
    Solvent molecules to solute molecules.
  • C
    Solute molecules to the total number of molecules to the total number of molecules in solution.
  • D
    Solvent molecules to the total number of molecules in solution.
Answer
  1. Solute molecules to the total number of molecules to the total number of molecules in solution.

Explanation:

Relative lowering of vapour pressure. The vapour pressure of a liquid is the pressure of the vapor which is in equilibrium with that liquid. The vapour pressure of a solvent is lowered when a non-volatile solute is dissolved in it to form a solution.

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MCQ 1351 Mark
For which solution the value of Van't hoff factor is not equal to 1?
  • A
    Glucose
  • B
    Sugar
  • C
    Fructose
  • D
    Acetic acid
Answer
  1. Acetic acid

Explanation:

Glucose, sugar and fructose are non- electrolytes, acetic acid is weak elecrolyte and hence dissociates in hydrogen and acetate ions.

Colligative property depends on number of particles present in the solution.

van't Hoff factor is ratio of observed colligative property to theoretical colligative property.

Therefore, van't Hoff factor of acetic acid is greater than 1.

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MCQ 1361 Mark
Mole fraction of glycerine C3H5(OH)3 in solution containing 36g of water and 46g of glycerine is:
  • A
    0.46
  • B
    0.40
  • C
    0.20
  • D
    0.36
Answer
  1. 0.20
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MCQ 1371 Mark
An ideal binary solution is prepared by two liquids A and B, with $\text{P}^\circ_\text{A}>\text{P}^\circ_\text{B}.$Then:
  • A
    A - B interactions are stronger than A - A and B - B.
  • B
    A and B have same molecular masses.
  • C
    A - B interactions are similar to A - A and B - B interactions.
  • D
    Both A and B are non - polar substances.
Answer
  1. A - B interactions are similar to A - A and B - B interactions.

Explanation:

For an ideal binary solution containing two liquids A and B, A - B interactions are similar to A - A and B - B interactions.

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MCQ 1381 Mark
Which of the following would have the lowest vapor pressure in the pure state?
  • A
    Sodium hydroxide because of the strong interparticle forces of ionic solids
  • B
    Methanol because of the hydrogen bonding in the functional group along with the non-polar nature of the carbon hydrogen bonds
  • C
    Water because of the very strong hydrogen bonding in the substances
  • D
    Ammonia because of the unbonded pair of electrons on the central atom coupled with hydrogen bonding in the substance.
Answer
  1. Sodium hydroxide because of the strong interparticle forces of ionic solids

Explanation:

Sodium hydroxide have lowest vapour pressure in the pure state because of the strong interparticle forces of ionic solids and also non-volatile in nature.

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MCQ 1391 Mark
Henry’s law constant for molality of methane is benzene at 298K is 4.27 × 105mm Hg. The mole fraction of methane is nenzene at 298K under 760mm Hg is:
  • A
    1.78 × 10-3
  • B
    17.43
  • C
    0.114
  • D
    2.814
Answer
  1. 1.78 × 10-3
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MCQ 1401 Mark
A plant cell shrinks when it is kept in a:
  • A
    Hypotonic solution
  • B
    Hypertonic solution
  • C
    Isotonic solution
  • D
    Pure water
Answer
  1. Hypertonic solution
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MCQ 1411 Mark
Which one of the following is the ratio of the lowering of vapour pressure of 0.1M aqueous solutions of BaCl2​, NaCl and Al2​(SO4​)3​ respectively?
  • A
    3 : 2 : 5
  • B
    5 : 2 : 3
  • C
    5 : 3 : 2
  • D
    2 : 3 : 5
Answer
  1. 3 : 2 : 5

Explanation:

Lowering of vapour pressure is a colligative property. It depends on the number of particles of the solute.

$\text{BaCl}_2\rightleftharpoons\text{Ba}^{2+}+2\text{Cl}^−; 3\text{ions}$

$\text{NaCl}\rightleftharpoons\text{Na}^++\text{Cl}^−; 2\text{ions}$

$\text{Al}_2​(\text{SO}_4​)_3\rightleftharpoons2\text{Al}^{3+}+3\text{SO}^{3-}_4​; 5\text{ions}$

Hence, the ratio of lowering of vapour pressure is 3 : 2 : 5 since the concentration of the solutions are same.

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MCQ 1421 Mark
50L of a certain liquid is confined in a piston system at the external pressure 100 atm. This pressure is suddenly released and liquid is expanded against the constant one atmosphere pressure, volume of the liquid increases by 1L and the final pressure on the liquid is 10atm. Find the magnitude of work done.
  • A
    1L atm
  • B
    5L atm
  • C
    50L atm
  • D
    500L atm
Answer
  1. 1L atm
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MCQ 1431 Mark
Raoult's law is obeyed by each constituent of a binary liquid solution when:
  • A
    The forces of attractions between like molecules are greater than those between unlike molecules.
  • B
    The forces of attractions between like molecules are smaller than those between unlike molecules.
  • C
    The forces of attractions between like molecules are identical with those between unlike molecules.
  • D
    The volume occupied by unlike molecules are different.
Answer
  1. The forces of attractions between like molecules are identical with those between unlike molecules.

Explanation:

When the forces of attractions between like molecules are identical with those between unlike molecules, Raoult's law is obeyed by each constituent of a binary liquid solution.

In such case, the total vapour pressure of the solution is the sum of the partial vapour pressures of components of the solution.

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MCQ 1441 Mark
Low concentration of oxygen in the blood and tissues of people living at high altitude is due to ____________.
  • A
    Low temperature.
  • B
    Low atmospheric pressure.
  • C
    High atmospheric pressure.
  • D
    Both low temperature and high atmospheric pressure.
Answer
  1. Low atmospheric pressure.

Explanation:

At high altitude the atmospheric pressure is decreased &, due to low atmospheric pressure the solubility of oxygen in blood and tissues is reduced.

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MCQ 1451 Mark
The value of observed and calculated molecular weight of silver nitrate are 92.64 and 170 respectively. The degree of dissociation of silver nitrate is:
  • A
    60%
  • B
    83.5%
  • C
    46.7%
  • D
    60.23%
Answer
  1. 83.5%
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MCQ 1461 Mark
When 20g of napthoic acid (C11​H8​O2​) is dissolved in 50g of benzene (Kf​ = 1.72K kg/ mol), a freezing point depression of 2K is observed. The van't Hoff factor (i) is:
  • A
    0.5
  • B
    1
  • C
    2
  • D
    3
Answer
  1. 0.5
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MCQ 1481 Mark
A beaker contains a solution of substance ‘A’. Precipitation of substance ‘A’ takes place when small amount of ‘A’ is added to the solution. The solution is _________.
  • A
    Saturated.
  • B
    Supersaturated.
  • C
    Unsaturated.
  • D
    Concentrated.
Answer
  1. Supersaturated.

Explanation:

When small amount of solute is added to its solution and it does not dissolve and get precipitated then this solution is supersaturated solution.

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MCQ 1491 Mark
Out of molality (m), molarity (M), formality (F) and mole fraction (x), those which are independent of temperature are:
  • A
    M, m
  • B
    F, x
  • C
    m, x
  • D
    M, x
Answer
  1. m, x
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MCQ 1501 Mark
Atomic mass is equal to:
  • A
    Number of electrons of an atom.
  • B
    Sum of the numbers of electrons and protons of an atom.
  • C
    Sum of the numbers of neutrons and protons of an atom.
  • D
    None of these.
Answer
  1. Sum of the numbers of electrons and protons of an atom.
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