CBSE Class 12 Science Chemistry · Ch 1: Solutions

Topics in this test

Difficulty: 3 easy · 9 medium · 18 hard

Sample questions with answers

The first 5 questions of this free test.

1. Q1. Consider the following statements about an ideal solution: (i) It obeys Raoult's law over the entire range of concentration. (ii) The enthalpy of mixing $\Delta_{mix}H$ is zero. (iii) The volume of mixing $\Delta_{mix}V$ is positive. Which of the statements are correct?

   • A. (i) and (ii) only
   • B. (ii) and (iii) only
   • C. (i), (ii) and (iii)
   • D. (i) and (iii) only
   Solution

   For an ideal solution both $\Delta_{mix}H$ and $\Delta_{mix}V$ are zero and it obeys Raoult's law throughout, so only statements (i) and (ii) are correct.

2. Q2. Which set correctly matches the colligative property with the quantity it is used to determine or the equation it follows? (i) Osmotic pressure — $\Pi = CRT$ (ii) Elevation of boiling point — $\Delta T_b = K_b m$ (iii) Depression of freezing point — $\Delta T_f = K_f m$

   • A. (i), (ii) and (iii) are all correct
   • B. Only (ii) and (iii) are correct
   • C. Only (i) is correct
   • D. Only (i) and (ii) are correct
   Solution

   All three relations are standard colligative-property equations where $C$ is molar concentration and $m$ is molality, so all are correctly matched.

3. Q3. Assertion (A): When red blood cells are placed in a solution containing more than 0.9% (mass/volume) sodium chloride, they shrink. Reason (R): In a hypertonic solution water flows out of the cells through the cell membrane by osmosis. Choose the correct option.

   • A. A is true but R is false
   • B. A is false but R is true
   • C. Both A and R are true and R is the correct explanation of A
   • D. Both A and R are true but R is not the correct explanation of A
   Solution

   A solution stronger than 0.9% NaCl is hypertonic, so water moves out of the cells causing them to shrink; both statements are true and R correctly explains A.

4. Q4. The freezing point depression of a 0.1 molal solution of acetic acid in benzene is found to be nearly half of that expected for 0.1 molal. The most likely reason is that acetic acid in benzene

   • A. undergoes association to form dimers, giving $i \approx \frac{1}{2}$
   • B. becomes non-volatile and does not affect freezing point
   • C. reacts chemically with benzene to form a new compound
   • D. undergoes dissociation into ions, giving $i \approx 2$
   Solution

   Acetic acid molecules associate into dimers through hydrogen bonding in benzene, reducing the number of particles so the van't Hoff factor is about $\frac{1}{2}$.

5. Q5. 0.1 molal aqueous solutions of the following solutes are prepared. Which solution will have the highest boiling point (assume complete dissociation for electrolytes)?

   • A. $\text{Al}_2(\text{SO}_4)_3$
   • B. $\text{CaCl}_2$
   • C. Glucose
   • D. $\text{NaCl}$
   Solution

   Boiling point elevation depends on the van't Hoff factor $i$; $\text{Al}_2(\text{SO}_4)_3$ gives $i=5$ ions, the largest number of particles, so the greatest elevation.

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