CBSE Class 12 Chemistry Solutions MCQs Set 06

Question. A solution containing components A and B follows Raoult’s law
(a) A – B attraction force is greater than A – A and B – B
(b) A – B attraction force is less than A – A and B – B
(c) A – B attraction force remains same as A – A and B – B
(d) volume of solution is different from sum of volume of solute and solvent.

Answer : C

Question. All form ideal solution except
(a) C₆H₆ and C₆H₅CH₃
(b) C₂H₆ and C₂H₅I
(c) C₆H₅Cl and C₆H₅Br
(d) C₂H₅I and C₂H₅OH

Answer : D

Question. An ideal solution is formed when its components
(a) have no volume change on mixing
(b) have no enthalpy change on mixing
(c) have both the above characteristics
(d) have high solubility.

Answer : C

Question. The freezing point depression constant (Kf) of benzene is 5.12 K kg mol^–1. The freezing point depression for the solution of molality 0.078 m containing a non-electrolyte solute in benzene is (rounded off upto two decimal places)
(a) 0.20 K
(b) 0.80 K
(c) 0.40 K
(d) 0.60 K

Answer : C

Question. If molality of the dilute solution is doubled, the value of molal depression constant (Kf) will be
(a) halved
(b) tripled
(c) unchanged
(d) doubled.

Answer : C

Question. At 100°C the vapour pressure of a solution of 6.5 g of a solute in 100 g water is 732 mm. If Kb = 0.52, the boiling point of this solution will be
(a) 102 °C
(b) 103 °C
(c) 101 °C
(d) 100 °C

Answer : C

Question. 200 mL of an aqueous solution of a protein contains its 1.26 g. The osmotic pressure of this solution at 300 K is found to be 2.57 × 10^–3 bar. The molar mass of protein will be (R = 0.083 L bar mol^–1 K^–1)
(a) 51022 g mol^–1
(b) 122044 g mol^–1
(c) 31011 g mol^–1
(d) 61038 g mol^–1

Answer : D

Question. A solution of sucrose (molar mass = 342 g mol^–1) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be (Kf for water = 1.86 K kg mol^–1)
(a) – 0.372 °C
(b) – 0.520 °C
(c) + 0.372 °C
(d) – 0.570 °C

Answer : A

Question. During osmosis, flow of water through a semipermeable membrane is
(a) from solution having lower concentration only
(b) from solution having higher concentration only
(c) from both sides of semipermeable membrane with equal flow rates
(d) from both sides of semipermeable membrane with unequal flow rates.

Answer : A

Question. If 0.15 g of a solute, dissolved in 15 g of solvent, is boiled at a temperature higher by 0.216°C, than that of the pure solvent. The molecular weight of the substance (Molal elevation constant for the solvent is 2.16°C) is
(a) 10.1
(b) 100
(c) 1.01
(d) 1000

Answer : B

Question. The van’t Hoff factor of BaCl₂ at 0.01 M concentration is 1.98. The percentage of dissociation of BaCl₂ at this concentration is 
(a) 4
(b) 69
(c) 89
(d) 98

Answer : A

Question. One gram of silver gets distributed between 10 cm³ of molten zinc and 100 cm³ of molten lead at 800°C. The percentage of silver still left in the lead layer in approximately. Distributed coefficient = 300 
(a) 2
(b) 5
(c) 3
(d) 1

Answer : C

Question. Which of the following is incorrect?
(a) Relative lowering of vapour pressure is independent of the nature of the solute and the solvent.
(b) The relative lowering of vapour pressure is a colligative property.
(c) Vapour pressure of a solution is lower than the vapour pressure of the sol vent.
(d) The relative lowering of vapour pressure is directly proportional to the original pressure.

Answer : D

Question. X is dissolved in water. Maximum boiling point is observed when X is … (0.1 M each)
(a) CaSO₄
(b) BaCl₂
(c) NaCl
(d) urea

Answer : B

Question. Which one of the following concentration units is independent of temperature ?
(a) Normality
(b) Molarity
(c) Molality
(d) ppm

Answer : C

Question. Solution A contains 7 g/L of MgCl₂ and solution B contains 7 g/L of NaCl. At room temperature, the osmotic pressure of 
(a) solution A is greater than B
(b) both have same osmotic pressure
(c) solution B is greater than A
(d) cannot be determine

Answer : C

Question. At certain temperature a 5.12% solution of cane sugar is isotonic with a 0.9% solution of an unknown solute. The molar mass of solute is
(a) 60
(d) 90
(b) 46.17
(e) 92.34
(c) 120

Answer : A

Question. The density (in g mL^-1) of a 3.60 M sulphuric acid solution that is 29% H₂SO₄ (molar mass = 98 g mol^-1 ) by mass will be 
(a) 1.64
(b) 1.88
(c) 1.22
(d) 1.45

Answer : C

Question. Abnormal colligative properties are observed only when the dissolved non-volatile solute in a given dilute solution
(a) is a non-electrolyte
(b) offers an intense colour
(c) associates or dissociates
(d) offers no colour

Answer : C

Question. Phenol dimerises in benzene having van’t Hoff factor 0.54. What is the degree of association ?
(a) 1.92
(b) 0.98
(c) 1.08
(d) 0.92

Answer : D

Question. Osmotic pressure observed when benzoic acid is dissolved in benzene is less than that expected from theoretical considerations. This is because
(a) benzoic acid is an organic solute
(b) benzoic acid bas higher molar mass than benzene
(c) benzoic acid gets associated in benzene
(d) benzoic acid gets dissociated in benzene

Answer : C

Question. When 20 g ofnaphthoic acid (C₁₁H₈O₂ )is dissolved in 50 g of benzene ( K_f = 1.72 K kg mol^-1 ), a freezing point depression of 2 ‘lis observed. The van’t Hoff factor (i) is
(a) 0.5
(b) 1
(c) 2
(d) 3

Answer : A

Question. Observe the following abbreviations π_obs = observed colligative property, π_cal = theoretical colligative property assuming normal behaviour of solute. van ‘t Hoff factor (i) is given by 
(a) i = π_obs X π_cal
(b) i = π_obs + π_cal
(c) i = π_obs – π_cal
(d) i = π_obs / π_cal

Answer : D

Question. 1.00 g of a non-electrolyte solute (molar mass 250 g mol^–1) was dissolved in 51.2 g of benzene. If the freezing point constant, Kf of benzene is 5.12 K kg mol^–1, the freezing point of benzene will be lowered by
(a) 0.2 K
(b) 0.4 K
(c) 0.3 K
(d) 0.5 K

Answer : B

Question. A solution containing 10 g per dm3 of urea (molecular mass = 60 g mol^–1) is isotonic with a 5% solution of a non-volatile solute. The molecular mass of this non-volatile solute is
(a) 200 g mol^–1
(b) 250 g mol^–1
(c) 300 g mol^–1
(d) 350 g mol^–1

Answer : C

Question. A solution of urea (mol. mass 56 g mol^–1) boils at 100.18°C at the atmospheric pressure. If Kf and Kb for water are 1.86 and 0.512 K kg mol^–1 respectively, the above solution will freeze at
(a) 0.654°C
(b) – 0.654°C
(c) 6.54°C
(d) – 6.54°C

Answer : B

Question. Pure water can be obtained from sea water by
(a) centrifugation
(b) plasmolysis
(c) reverse osmosis
(d) sedimentation.

Answer : C

Question. From the colligative properties of solution, which one is the best method for the determination of molecular weight of proteins and polymers?
(a) Osmotic pressure
(b) Lowering in vapour pressure
(c) Lowering in freezing point
(d) Elevation in boiling point

Answer : A

Question. The vapour pressure of benzene at a certain temperature is 640 mm of Hg. A non-volatile and non-electrolyte solid, weighing 2.175 g is added to 39.08 of benzene. The vapour pressure of the solution is 600 mm of Hg. What is the molecular weight of solid substance?
(a) 69.5
(b) 59.6
(c) 49.50
(d) 79.8

Answer : A

Question. The elevation in boiling point of a solution of 13.44 g of CuCl₂ in 1 kg of water using the following infom1ation will be (molecular weight of CuCl₂ = 134. 4 and k_b = 0.52Km^-1) 
(a) 0.16
(b) 0.05
(c) 0.1
(d) 0.2

Answer : A

Question. Distribution law was given by
(a) Henry
(b) van’t Hoff
(c) Nemst’s
(d) Ostwald

Answer : C

Question. If α is the degree of dissociation of Na₂SO₄, the Vant Hoff’s factor (i) used for calculating the molecular mass is
(a) 1 – 2α
(b) 1 + 2α
(c) 1 – α
(d) 1 + α

Answer : B

Question. Which bas minimum osmotic pressure ?
(a) 200 mL of 2 M NaCl solution
(b) 200 mL of 1 M glucose solution
(c) 200 mL of 2 M urea solution
(d) All have same osmotic pressure

Answer : B

Question. The vapour pressure will be lowest for
(a) 0. 1 M sugar solution
(b) 0.1 M KCl solution
(c) 0. 1 M Cu(NO3 )2 solution
(d) 0.1 M AgNO3 solution

Answer : C

Question. Osmotic pressure of 0.4% urea solution is 1.64 atrn and that of 3.42% cane sugar is 2.46 atm. When the above two solutions are mixed, the osmotic pressure of the resulting solution is
(a) 0.82 atrn
(b) 2.46 atm
(c) 1.64 atm
(d) 4.10 atm

Answer : D

Question. Which condition is not satisfied by an ideal solution?
(a) DmixV = 0
(b) DmixS = 0
(c) Obeyance to Raoult’s Law
(d) DmixH = 0

Answer : B

Question. A solution of acetone in ethanol
(a) obeys Raoult’s law
(b) shows a negative deviation from Raoult’s law
(c) shows a positive deviation from Raoult’s law
(d) behaves like a near ideal solution.

Answer : C