Solutions

36 NEET-UG practice questions on Solutions, part of Chemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   Examine these statements about non-ideal solutions. A. A solution showing positive deviation has Δ_mix H > 0 and Δ_mix V > 0. B. A maximum boiling azeotrope forms from a large positive deviation. C. A mixture of chloroform and acetone shows negative deviation from Raoult's law. D. In an ideal solution, A–B interactions are of about the same strength as A–A and B–B interactions. Choose the option listing the correct statements.

   1. AA, C and D only
   2. BA, B and C only
   3. CA and C only
   4. DB and D only

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   Answer: A · A, C and D only

   Weaker A–B attractions give positive deviation with heat absorbed and volume expansion, so A is true. A large positive deviation gives a minimum boiling azeotrope, so B is false. Chloroform hydrogen-bonds to acetone (negative deviation), and D defines an ideal solution.

   • B: Accepts B, which has the azeotrope type reversed, and leaves out D.
   • C: Leaves out D, which is the definition of an ideal solution.
   • D: Accepts B and rejects A and C, which are both true.

   Remember this

   Large positive deviation gives a minimum boiling azeotrope; large negative deviation gives a maximum boiling one.

2. Question 2 · Easy

   A solution is made by dissolving 4.0 g of NaOH in enough water to give 250 mL of solution. What is its molarity? (Molar mass of NaOH = 40 g/mol.)

   1. A16 M
   2. B0.025 M
   3. C0.10 M
   4. D0.40 M

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   Answer: D · 0.40 M

   Moles of NaOH = 4.0/40 = 0.10 mol. Molarity = 0.10/0.250 L = 0.40 M.

   • A: Divides grams by litres, which gives g/L and not mol/L.
   • B: Multiplies moles by the volume instead of dividing.
   • C: Stops at the number of moles and ignores the volume.

   Remember this

   Molarity uses litres of solution, so divide moles by volume in litres and never multiply.

3. Question 3 · Easy

   Gases X and Y are kept over water at the same temperature and the same partial pressure. If the Henry's law constant of X is larger than that of Y, then X is

   1. Ainsoluble in water at this pressure
   2. Bequally soluble in water as Y
   3. Cless soluble in water than Y
   4. Dmore soluble in water than Y

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   Answer: C · less soluble in water than Y

   Henry's law is p = K_H x, so x = p/K_H. At a fixed p, a larger K_H means a smaller mole fraction of the gas in solution.

   • A: A larger K_H lowers the solubility but does not make it zero.
   • B: Ignores K_H, which differs between the gases.
   • D: Reads K_H as a direct measure of solubility; it varies inversely.

   Remember this

   Higher K_H means lower solubility; K_H also rises with temperature, so gases dissolve less on warming.

4. Question 4 · Medium

   Find the boiling point of a solution of 5.85 g of NaCl in 500 g of water, assuming complete dissociation. (NaCl = 58.5 g/mol; K_b of water = 0.52 K kg/mol; boiling point of water = 100.000 °C.)

   1. A100.208 °C
   2. B100.104 °C
   3. C100.052 °C
   4. D100.416 °C

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   Answer: A · 100.208 °C

   Moles of NaCl = 0.10, so m = 0.10/0.500 = 0.20 m. With i = 2, ΔT_b = 2 × 0.52 × 0.20 = 0.208 K, which gives 100.208 °C.

   • B: Ignores the van't Hoff factor and takes i = 1.
   • C: Uses 0.10 mol as the molality and also takes i = 1.
   • D: Doubles the molality as well as applying i = 2.

   Remember this

   For an electrolyte use ΔT_b = i K_b m; NaCl has i = 2 when fully dissociated.

5. Question 5 · Medium

   An aqueous NaOH solution is 20% by mass. What is its molality? (Molar mass of NaOH = 40 g/mol.)

   1. A0.625 m
   2. B4.00 m
   3. C6.25 m
   4. D5.00 m

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   Answer: C · 6.25 m

   In 100 g of solution there are 20 g NaOH (0.50 mol) and 80 g water. Molality = 0.50/0.080 kg = 6.25 m.

   • A: Slips a factor of ten in converting grams to kilograms.
   • B: Takes the ratio of the two masses, 80/20, in place of moles per kilogram.
   • D: Divides by 100 g of solution instead of 80 g of solvent.

   Remember this

   Molality divides by the mass of solvent alone, so subtract the solute from the solution first.

6. Question 6 · Medium

   A solution containing 2.0 g of a protein in 200 mL of solution has an osmotic pressure of 0.0083 bar at 27 °C. Determine the molar mass of the protein. (Take R = 0.083 L bar K⁻¹ mol⁻¹.)

   1. A2700 g/mol
   2. B30000 g/mol
   3. C6000 g/mol
   4. D150000 g/mol

   Answer and explanation in LearnFree account

7. Question 7 · Easy

   Arrange these aqueous solutions in increasing order of freezing point, assuming complete dissociation of the salts. A. 0.1 m KCl B. 0.1 m glucose C. 0.1 m Al₂(SO₄)₃ D. 0.1 m K₂SO₄

   1. AB, A, D, C
   2. BD, C, A, B
   3. CC, D, A, B
   4. DC, A, D, B

   Answer and explanation in LearnFree account

8. Question 8 · Medium

   Match List-I with List-II for dilute aqueous solutions, assuming complete dissociation of the ionic compounds. List-I (solute) A. Urea B. MgSO₄ C. CaCl₂ D. K₄[Fe(CN)₆] List-II (van't Hoff factor) I. 3 II. 1 III. 5 IV. 2

   1. AA-II, B-IV, C-III, D-I
   2. BA-II, B-I, C-IV, D-III
   3. CA-II, B-IV, C-I, D-III
   4. DA-IV, B-II, C-I, D-III

   Answer and explanation in LearnFree account

9. Question 9 · Medium

   Assertion A: Aquatic species are more comfortable in cold water than in warm water. Reason R: The solubility of oxygen in water increases with a rise in temperature. Choose the correct answer.

   1. ABoth A and R are correct but R is not the correct explanation of A
   2. BBoth A and R are correct and R is the correct explanation of A
   3. CA is correct but R is not correct
   4. DA is not correct but R is correct

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    Water has a vapour pressure of 760 mmHg at 100 °C. If 18 g of glucose is dissolved in 178.2 g of water, what is the vapour pressure of the solution at this temperature? (Glucose = 180 g/mol, water = 18 g/mol.)

    1. A744.8 mmHg
    2. B7.6 mmHg
    3. C752.4 mmHg
    4. D684.0 mmHg

    Answer and explanation in LearnFree account

11. Question 11 · Hard

    Benzoic acid dimerises in benzene. A solution of 6.1 g of benzoic acid (M = 122 g/mol) in 50 g of benzene shows a freezing point depression of 4.0 K. Taking K_f of benzene as 5.0 K kg/mol, what percentage of the acid is dimerised?

    1. A20%
    2. B40%
    3. C60%
    4. D80%

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12. Question 12 · Medium

    Liquids A and B form an ideal solution. At a given temperature, their pure vapour pressures are 120 mmHg and 40 mmHg. For a liquid mixture with mole fraction of A = 0.25, the mole fraction of A in the vapour is

    1. A0.33
    2. B0.50
    3. C0.25
    4. D0.75

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13. Question 13 · Medium

    Given below are two statements: Statement I: Solutions that show a large negative deviation from Raoult's law form minimum boiling azeotropes. Statement II: Ethanol and water form a minimum boiling azeotrope at about 95% ethanol by volume. Choose the correct answer.

    1. AStatement I is incorrect but Statement II is correct
    2. BStatement I is correct but Statement II is incorrect
    3. CBoth Statement I and Statement II are incorrect
    4. DBoth Statement I and Statement II are correct

    Answer and explanation in LearnFree account

14. Question 14 · Easy

    Two liquids are mixed, and the vapour pressure of the mixture turns out lower than Raoult's law predicts. Which pair could these liquids be?

    1. ACarbon disulphide and acetone
    2. BChloroform and acetone
    3. CBenzene and toluene
    4. DEthanol and acetone

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15. Question 15 · Hard

    A 0.20 m aqueous solution of a weak monobasic acid HA freezes at −0.4092 °C. Taking K_f of water as 1.86 K kg mol⁻¹, what is the degree of dissociation of HA?

    1. A9.1%
    2. B5%
    3. C10%
    4. D90%

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16. Question 16 · Medium

    At 298 K the Henry's law constant, K_H, of nitrogen in water is 8.0 × 10⁴ bar. If the partial pressure of nitrogen over the water is 0.80 bar, what is the mole fraction of dissolved nitrogen?

    1. A1.0 × 10⁻⁵
    2. B1.0 × 10⁵
    3. C1.0 × 10⁻⁴
    4. D6.4 × 10⁴

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17. Question 17 · Medium

    An aqueous solution contains 6 g of urea (molar mass 60 g mol⁻¹) per litre. What mass of glucose (molar mass 180 g mol⁻¹) per litre makes a solution isotonic with it at the same temperature?

    1. A18 g
    2. B2 g
    3. C36 g
    4. D6 g

    Answer and explanation in LearnFree account

18. Question 18 · Medium

    Given below are two statements: Statement I: Dissolution of a gas in a liquid is endothermic, so the solubility of gases in liquids increases with temperature. Statement II: Scuba divers breathe air diluted with helium because helium is more soluble in blood than nitrogen. Choose the correct answer.

    1. ABoth Statement I and Statement II are incorrect
    2. BStatement I is correct but Statement II is incorrect
    3. CStatement I is incorrect but Statement II is correct
    4. DBoth Statement I and Statement II are correct

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19. Question 19 · Medium

    Match List-I with List-II. List-I (Term) A. Ideal solution B. Positive deviation from Raoult's law C. Negative deviation from Raoult's law D. Reverse osmosis List-II (Description) I. A–B attractions weaker than A–A and B–B attractions II. ΔmixH = 0 and ΔmixV = 0 III. Can form a maximum-boiling azeotrope IV. Used to desalinate sea water Choose the correct answer from the options given below.

    1. AA-II, B-I, C-III, D-IV
    2. BA-II, B-III, C-I, D-IV
    3. CA-II, B-I, C-IV, D-III
    4. DA-I, B-II, C-III, D-IV

    Answer and explanation in LearnFree account

20. Question 20 · Hard

    Dissolving 5.0 g of a non-volatile, non-electrolyte solute in 39 g of benzene lowers the vapour pressure of benzene from 640 mmHg to 600 mmHg at a certain temperature. Using the exact relation (p° − p)/p° = mole fraction of solute, find the molar mass of the solute. (Benzene = 78 g mol⁻¹)

    1. A75 g mol⁻¹
    2. B140 g mol⁻¹
    3. C150 g mol⁻¹
    4. D160 g mol⁻¹

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21. Question 21 · Medium

    What mass of ethylene glycol (C₂H₆O₂, molar mass 62 g mol⁻¹) must be dissolved in 1.0 kg of water to lower its freezing point by 3.72 K? (Kf of water = 1.86 K kg mol⁻¹; ethylene glycol is a non-electrolyte.)

    1. A124 g
    2. B248 g
    3. C31 g
    4. D62 g

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22. Question 22 · Easy

    Which of the following is a colligative property of a dilute solution of a non-volatile solute?

    1. ADensity of the solution
    2. BOsmotic pressure
    3. CVapour pressure of the solution
    4. DBoiling point of the solution

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23. Question 23 · Easy

    Which pair of liquids forms a non-ideal solution showing positive deviation from Raoult's law?

    1. AChloroform and acetone
    2. BBenzene and toluene
    3. CEthanol and acetone
    4. Dn-Hexane and n-heptane

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24. Question 24 · Easy

    Warming a solution changes its volume. Which concentration term stays the same when a solution is warmed?

    1. AMolarity
    2. BVolume percentage
    3. CMass by volume percentage
    4. DMolality

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25. Question 25 · Hard

    Liquids A and B form an ideal solution; p°A = 300 mmHg and p°B = 100 mmHg. The vapour above an equimolar liquid mixture is collected and fully condensed, and the condensate is allowed to reach equilibrium with its own vapour. What is the mole fraction of A in this new vapour?

    1. A0.75
    2. B0.60
    3. C0.50
    4. D0.90

    Answer and explanation in LearnFree account