CBSE Class 12 Chemistry Solutions MCQs Set A

Question : An aqueous solution of hydrochloric acid

a) Obeys Raoult’s law
b) Shows negative deviation from Raoult’s law
c) Shows positive deviation from Raoult’s law
d) Obeys Henry’s law at all compositions

Answer : B

Question : Exactly 1 g of urea dissolved in 75 g of water gives a solution that boils at 100.114°C at 760 torr. The molecular weight of urea is 60.1. The boiling point elevation constant for water is

a) 1.02 b) 0.51
c) 3.06 d) 1.51

Answer : B

Question :   12g of urea is dissolved in 1 litre of water and 68.4 g of sucrose is dissolved in 1 litre of water. The lowering of vapour pressure of first case is

a) equal to second
b) greater than second
c) less than second
d) double that of second

Answer : A

Question : At a particular temperature, the vapour pressures of two liquids A and B are respectively 120 and 180 mm of mercury. If 2 moles of A and 3 moles of B are mixed to form an ideal solution, the vapour pressure of the solution at the same temperature will be (in mm of mercury)

a) 156 b) 145
c) 150 d) 108

Answer : A

Question : The freezing point of equimolal aqueous solution will be highest for

a) C₆H₅NH₃ ⁺Cl^–   b) Ca(NO₃)₂
c) La(NO₃)₂         d) C₆H₁₂O₆

Answer : D

Question : Which of the following 0.10 m aqueous solutions will have the lowest freezing point ?

a) Al₂(SO₄)₃ b) C₆H₁₂O₆
c) KCl            d) C₁₂H₂₂O₁₁

Answer : A

Question : A solution containing 10g per dm³ of urea (molecular mass = 60 gmol^–1) is isotonic with a 5% solution of a non volatile solute. The molecular mass of this non volatile solute is

a) 300 g mol^–1 b) 350 g mol^–1
c) 200 g mol^–1 b) 250 g mol^–1

Answer : A 

Question : The vapour pressure of a solvent decreases by 10 mm of Hg when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.2. What should be the mole fraction of the solvent if the decrease in
the vapour pressure is to be 20 mm of Hg ?

a) 0.8 b) 0.6
c) 0.4 d) 0.2

Answer : B

Question : A solution containing 1.8 g of a compound (empirical formula CH₂O) in 40 g of water is observed to freeze at –0.465° C. The molecular formula of the compound is (K_f of water = 1.86 kg K mol^–1)

a) C₂H₄O₂ b) C₃H₆O₃
c) C₄H₈O₄ d) C₆H₁₂O₆

Answer : D

Question : 10 Which observation(s) reflect(s) colligative properties?
(i) A 0.5 m NaBr solution has a higher vapour pressure than a 0.5 m BaCl₂ solution at the same temperature
(ii) Pure water freezes at the higher temperature than pure methanol
(iii) a 0.1 m NaOH solution freezes at a lower temperature than pure water

Choose the correct answer from the codes given below

a) (i), (ii) and (iii) b) (i) and (ii)
c) (ii) and (iii)       d) (i) and (iii)

Answer : D

Question : The vapour pressure of benzene at 30°C is 121.8 mm. By adding 15 g of non-volatile solute in 250 g of benzene, its vapour pressure is decreased to 120.2 mm. The molecular weight of solute is :

a) 156.6 g b) 267.4 g
c) 356.3 g d) 467.4 g

Answer : C

Question : Pure benzene freezes at 5.45°C. A 0.374 m solution of tetrachloroethane in benzene freezes at 3.55°C. The Kf for benzene is:

a) 0.508 b) 5.08
c) 50.8   d) 508

Answer : B

Question : 0.450 g of urea (mol.wt.60) in 22.5 g of water show 0.170°C of elevation in boiling point. The molal elevation constant of water is:

a) 0.051°C b) 0.51°C
c) 5.1°C     d) 0.83°C

Answer : B

Question : The colligative property is not represented by :

a) elevation in boiling point
b) osmotic pressure
c) optical activity
d) relative lowering of vapour pressure

Answer : C

Question : 20 g of a substance were dissolved in 500 mL of water and the osmotic pressure of the solution was found to be 600 mm of mercury at 15°C. The molecular weight of substance is :

a) 998   b) 1028
c) 1098 d) 1198

Answer : D

Question : Which one of the statements given below concerning properties of solutions, describes a colligative effect?

a) Boiling point of pure water decreases by the addition of ethanol
b) Vapour pressure of pure water decreases by the addition of nitric acid
c) Vapour pressure of pure benzene decreases by the addition of naphthalene
d) Boiling point of pure benzene increases by the addition of toluene

Answer : C

Question : The average osmotic pressure of human blood is 7.8 bar at 37°C. What is the concentration of an aqueous NaCl solution that could be used in the blood stream?

a) 0.16 mol/L   b) 0.31 mol / L
c) 0.60 mol / L d) 0.45 mol / L

Answer : B

Question : A 5% solution (by mass) of cane sugar in water has freezing point of 271 K and freezing point of pure water is 273.15 K. The freezing point of a 5% solution (by mass) of glucose in water is

a) 271 K     b) 273.15K
c) 269.07 K d) 277.23 K

Answer : C

Question : The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile, nonelectrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g/mol). The vapour pressure of the solution then is 0.845 bar. What is the molecular mass of the solid substance? 

a) 58   b) 180
c) 170 d) 145.

Answer : C

Question : 0.01 M solution of KCl and BaCl2 are prepared in water. The freezing point of KCl is found to be –2°C. What is the freezing point of BaCl2 to be completely ionised ?

a) – 3°C b) + 3°C
c) – 2°C d) – 4°C

Answer : A

Question : “The importance of many pure substance in life depends on their composition.” Which of the following statement justify the above fact?

a) 1 ppm of fluoride ions in water prevents tooth decay.

b) 1.5 ppm of fluoride ions causes tooth decay.

c) Concentration above 1.5 ppm can be poisonous.

d) All of the above.

Question : Which of the following fluoride is used as rat poison?

a) CaF₂ b) KF

c) NaF d) MgF₂

Question : Most of the processes in our body occur in

a) solid solution b) liquid solution

c) gaseous solution d) colloidal solution

Question : The term homogenous mixtures signifies that

a) its composition is uniform throughout the mixture.

b) its properties are uniform throughout the mixture.

c) both composition and properties are uniform throughout the mixture.

d) neither composition nor properties are uniform throughout the mixture.

Question : Which of the following mixture is(are) called solution?

(i) water + ammonia (ii) water + acetone

(iii) acetone + alcohol (iv) hexane + water

a) (i), (ii) and (iii) b) (i), (iii) and (iv)

c) (i) and (iv) d) (ii) and (iii)

Question : Which of the following is a quantitative description of the solution?

a) Dilute b) Concentrated

c) Saturated d) Molar

Question : When a solute is present in trace quantities the following expression is used

a) Gram per million b) Milligram percent

c) Microgram percent d) Parts per million

Question : Molarity of liquid HCl will be, if density of solution is 1.17 gm/cc

a) 36.5 b) 32.05

c) 18.25 d) 42.10

Question : 1 M, 2.5 litre NaOH solution is mixed with another 0.5 M, 3 litre NaOH solution. Then find out the molarity of resultant solution

a) 0.80 M b) 1.0 M

c) 0.73 M d) 0.50 M

Question : An X molal solution of a compound in benzene has mole fraction of solute equal to 0.2. The value of X is

a) 14 b) 3.2

c) 1.4 d) 2

Question : The molarity of the solution containing 7.1 g of Na2SO4 in 100 ml of aqueous solution is

a) 2 M b) 0.5 M

c) 1 M d) 0.05 M

Question : The vapour pressure of pure benzene at 25°C is 640 mm Hg and that of solution of solute A is 630 mm Hg. The molality of solution is

a) 0.2 m b) 0.4 m

c) 0.5 m d) 0.1 m

Question : 4.0 g of NaOH is dissolved in 100 ml solution. The normality of the solution is

a) 0.1 N b) 0.5 N

c) 4.0 N d) 1.0 N

Question : The molarity of pure water is

a) 50 M b) 18 M

c) 55.6 M d) 100 M

Question : An aqueous solution of glucose is 10% in strength. The volume in which 1 g mole of it is dissolved, will be

a) 9 litre b) 1.8 litre

c) 8 litre d) 0.9 litre

Question : 10 g of NaCl is dissolved in 106g of the solution. Its concentration is

a) 100 ppm b) 0.1 ppm

c) 1 ppm d) 10 ppm

Question : On adding a solute to a solvent having vapour pressure 0.80 atm, vapour pressure reduces to 0.60 atm. Mole fraction of solute is

a) 0.25 b) 0.75

c) 0.50 d) 0.33

Question : 2.5 litres of NaCl solution contain 5 moles of the solute. What is the molarity?

a) 5 molar b) 2 molar

c) 2.5 molar d) 12.5 molar

Question : The mole fraction of the solute in one molal aqueous solution i

a) 0.009 b) 0.018

c) 0.027 d) 0.036

Question : 5 ml of N HCl, 20 ml of N/2 H2SO4 and 30 ml of N/3 HNO3 are mixed together and volume made to one litre. The normality of the resulting solution is

a)N5

b)N10

c)N20

d) N/40

Question : 25ml of a solution of barium hydroxide on titration with a 0.1 molar solution of hydrochloric acid gave a titre value of 35ml. The molarity of barium hydroxide solution was

a) 0.07 b) 0.14

c) 0.28 d) 0.35

Question : Mole fraction of the solute in a 1.00 molal aqueous solution is

a) 0.1770 b) 0.0177

c) 0.0344 d) 1.7700

Question : What is the normality of a 1 M solution of H3PO4 ?

a) 0.5 N b) 1.0 N

c) 2.0 N d) 3.0 N

Question : The volume of 4 N HCl and 10 N HCl required to make 1 litre of 6 N HCl are

a) 0.75 litre of 10 N HCl and 0.25 litre of 4 N HCl

b) 0.50 litre of 4 N HCl and 0.50 litre of 10 N HCl

c) 0.67 litre of 4 N HCl and 0.33 litre of 10 N HCl

d) 0.80 litre of 4 N HCl and 0.20 litre of 10 N HCl

Question : Molarity of H2SO4 is 18 M. Its density is 1.8 g/ml. Hence molality is

a) 36 b) 200

c) 500 d) 18

Question : 200 ml of water is added to 500 ml of 0.2 M solution. What is the molarity of this diluted solution ?

a) 0.5010 M b) 0.2897 M

c) 0.7093 M d) 0.1428 M

Question : How many grams of concentrated nitric acid solution should be used to prepare 250 mL of 2.0M HNO3 ? The concentrated acid is 70% HNO3

a) 90.0 g conc. HNO3 b) 70.0 g conc. HNO₃

c) 54.0 g conc. HNO3 d) 45.0 g conc. HNO₃

Question : For preparing 0.1 N solution of a compound from its impure sample of which the percentage purity is known, the weight of the substance required will be

a) Less than the theoretical weight

b) More than the theoretical weight

c) Same as the theoretical weight

d) None of these

Question : If N/10 50 ml H2SO4,N/3 30 ml HNO3, N/2 10 ml HCl is mixed and solution is made to 1L. Then normality of resultant solution is

a)N/20

b)N/40

c) 50/N

d) N

Question : A solution made by dissolving 40 g NaOH in 1000 g of water is

a) 1 molar b) 1 normal

c) 1 molal d) None of these

Question : Which of the following concentration terms is/are independent of temperature?

a) Molality only

b) Molality and mole fraction

c) Molarity and mole fraction

d) Molality and normality

Question : A solution is prepared by dissolving 10 g NaOH in 1250 mL of a solvent of density 0.8 mL/g. The molality of the solution in mol kg–1 is

a) 0.25 b) 0.2

c) 0.008 d) 0.0064

Question : Which of the following units is useful in relating concentration of solution with its vapour pressure?

a) mole fraction b) parts per million

c) mass percentage d) molality

Question : Which of the following concentration unit is independent of temperature ?

a) Normality b) Molarity

c) Formality d) Molality

Question : Which of the following factor do not affect solubility of solid solute in liquid ?

a) Temperature b) Pressure

c) Nature of solute d) All of these

Question : When a solid solute is added to the solvent, some solute dissolves and its concentration increases in solution. This process is known as ______. Some solute particles in solution collide with the solid solute particles and get separated out of solution. This process is known as ______.

a) Crystallization, dissolution.

b) Dissolution, saturation.

c) Saturation, crystallization.

d) Dissolution, crystallization.

Question : At the state of dynamic equilibrium, for solute + solvent solution.

a) Rate of dissolution = Rate of unsaturation.

b) Rate of dissolution = Rate of unsaturation.

c) Rate of dissolution = Rate of saturation

d) Rate of crystallization = Rate of saturation.

Question : Which of the following statements is incorrect?

a) A solution in which no more solute can be dissolved at the same temperature and pressure is called a saturated solution.

b) An unsaturated solution is one in which more solute can be dissolved at the same temperature.

c) The solution which is in dynamic equilibrium with undissolved solute is the saturated solution.

d) The minimum amount of solute dissolved in a given amount of solvent is its solubility.

Question : On dissolving sugar in water at room temperature solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid ?

a) Sugar crystals in cold water.

b) Sugar crystals in hot water.

c) Powdered sugar in cold water.

d) Powdered sugar in hot water.

Question : The solubility of a solid in a liquid is significantly affected by temperature changes.

Solute + Solvent → Solution.

The system being in a dynamic equilibrium must follow

Le-chatelier’s principle. Considering the Le-chatelier’s

principle which of the following is correct?

a) △H_sol > 0; solubility ↑ ; temperature ↓

b) △H_sol < 0; solubility ↓ ; temperature ↑

c) △H_sol > 0; solubility ↓; temperature ↑

d) △H_sol < 0; solubility ↓ ; temperature ↑

Question : The statement “If 0.003 moles of a gas are dissolved in 900 g of water under a pressure of 1 atmosphere, 0.006 moles will be dissolved under a pressure of 2 atmospheres”,illustrates

a) Dalton’s law of partial pressure

b) Graham’s law

c) Raoult’s law

d) Henry’s law

Question : According to Henry’s law, the amount of gas that will dissolve in blood plasma or any other liquid is determined by which of these factor?

a) Solubility of the gas in the liquid.

b) The total pressure of the gas mixture .

c) pH of the liquid.

d) The osmotic pressure of the gas mixture.

Question : Henry’s law constant of oxygen is 1.4 × 10–3 mol. lit–1. atm–1 at 298 K. How much of oxygen is dissolved in 100 ml at 298 K when the partial pressure of oxygen is 0.5 atm?

a) 1.4 g b) 3.2 g

c) 22.4 mg d) 2.24 mg

Question : At equillibrium 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

Question : 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

Question : Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon __________.

a) Temperature b) Nature of solute

c) Pressure d) Nature of solvent

Question : 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

Question : Value of Henry's constant KH _______.

a) increases with increase in temperature.

b) decreases with increase in temperature.

c) remains constant.

d) first increases then decreases.

Question : 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.

Question : Which of the followingfactor(s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent ?

(i) Nature of solute (ii) Temperature (iii) Pressure

a) (i) and (iii) at constant T

b) (i) and (ii) at constant P

c) (ii) and (iii) only

d) (iii) only