CBSE Class 12 MCQs Chemistry Chapter 2 Solutions

Class 12^th Chemistry Chapter MCQs

1. The maximum amount of solute that can be dissolved in a given solvent at a given temperature is known as:

a) Solubility
b) Concentration
c) Molarity
d) Molality

Answer: a) Solubility
Explanation: Solubility refers to the maximum amount of solute that can dissolve in a given solvent at a specific temperature.

2. The molality of a solution is defined as:

a) Moles of solute per liter of solution
b) Moles of solute per kilogram of solvent
c) Mass of solute per volume of solution
d) Volume of solute per mass of solvent

Answer: b) Moles of solute per kilogram of solvent
Explanation: Molality is the number of moles of solute per kilogram of solvent.

3. The effect of temperature on the solubility of gases in liquids is:

a) Solubility of gases increases with temperature
b) Solubility of gases decreases with temperature
c) Solubility remains unaffected by temperature
d) Solubility first increases and then decreases with temperature

Answer: b) Solubility of gases decreases with temperature
Explanation: As temperature increases, the solubility of gases in liquids decreases, because gases tend to escape from the solution at higher temperatures.

4. Which of the following is a colligative property?

a) Boiling point
b) Freezing point
c) Osmotic pressure
d) All of the above

Answer: d) All of the above
Explanation: Colligative properties, including boiling point elevation, freezing point depression, and osmotic pressure, depend on the number of solute particles in the solution, not their identity.

5. The vapor pressure of a solvent in an ideal solution depends on:

a) The temperature
b) The concentration of solute
c) The molecular weight of the solute
d) The polarity of the solvent

Answer: b) The concentration of solute
Explanation: In an ideal solution, the vapor pressure of the solvent decreases as the concentration of solute increases.

6. Which of the following statements is true for ideal solutions?

a) The enthalpy of mixing is zero
b) The volume change on mixing is zero
c) The solute and solvent obey Raoult's law
d) All of the above

Answer: d) All of the above
Explanation: Ideal solutions obey Raoult's law, have zero enthalpy of mixing, and no volume change upon mixing.

7. If the freezing point of a solution is 2°C, and the freezing point of the pure solvent is 5°C, what is the freezing point depression?

a) 2°C
b) 3°C
c) 5°C
d) 7°C

Answer: b) 3°C
Explanation: Freezing point depression is the difference between the freezing point of the pure solvent and the solution. So, 5°C - 2°C = 3°C.

8. In an ideal solution, the partial vapor pressure of the solvent is given by:

a) $P_1 = X_1 P_1^0$
b) $P_1 = X_2 P_1^0$
c) $P_1 = P_1^0 + P_2^0$
d) $P_1 = P_2^0 - X_2$

Answer: a) $P_1 = X_1 P_1^0$
Explanation: In an ideal solution, the partial vapor pressure of the solvent is directly proportional to its mole fraction $X_1$ and its vapor pressure in the pure state $P_1^0$ .

9. The total vapor pressure of a solution is the sum of the vapor pressures of the solute and solvent. This is called:

a) Raoult's Law
b) Henry's Law
c) Dalton's Law
d) Avogadro's Law

Answer: a) Raoult's Law
Explanation: Raoult's Law states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent in the solution.

10. Which of the following is the best method to separate a mixture of two liquids with different boiling points?

a) Filtration
b) Simple distillation
c) Fractional distillation
d) Chromatography

Answer: c) Fractional distillation
Explanation: Fractional distillation is used to separate mixtures of liquids with different boiling points.

11. The value of the van't Hoff factor ( $i$ ) for a non-electrolyte solute is:

a) 0
b) 1
c) 2
d) Infinite

Answer: b) 1
Explanation: For a non-electrolyte solute, which does not dissociate in solution, the van't Hoff factor ( $i$ ) is 1.

12. The molarity of a solution is:

a) Moles of solute per liter of solution
b) Moles of solute per kilogram of solvent
c) Mass of solute per volume of solution
d) Volume of solute per mass of solvent

Answer: a) Moles of solute per liter of solution
Explanation: Molarity is the number of moles of solute dissolved in one liter of solution.

13. A solution that has the same concentration as the cell's cytoplasm is called:

a) Hypertonic
b) Hypotonic
c) Isotonic
d) Saturated

Answer: c) Isotonic
Explanation: An isotonic solution has the same concentration of solute as the cytoplasm of a cell, which prevents the cell from swelling or shrinking.

14. The concentration of a solution in terms of molality is:

a) Moles of solute per liter of solution
b) Moles of solute per kilogram of solvent
c) Grams of solute per liter of solution
d) Grams of solute per kilogram of solvent

Answer: b) Moles of solute per kilogram of solvent
Explanation: Molality is expressed as moles of solute per kilogram of solvent.

15. The vapor pressure of a solution decreases when:

a) The temperature increases
b) The solute is added to the solvent
c) The solute is volatile
d) The solute is highly concentrated

Answer: b) The solute is added to the solvent
Explanation: Adding a non-volatile solute to a solvent lowers the vapor pressure of the solvent.

16. Which of the following is an example of an ideal solution?

a) Benzene and toluene
b) Water and ethanol
c) Acetone and chloroform
d) None of the above

Answer: a) Benzene and toluene
Explanation: Benzene and toluene form an ideal solution as they obey Raoult's law throughout all concentrations.

17. Which of the following is the correct expression for the depression in freezing point ( $\Delta T_f$ )?

a) $\Delta T_f = K_f \cdot m$
b) $\Delta T_f = K_b \cdot m$
c) $\Delta T_f = K_f \cdot m \cdot i$
d) $\Delta T_f = K_b \cdot m \cdot i$

Answer: c) $\Delta T_f = K_f \cdot m \cdot i$
Explanation: The depression in freezing point is given by $\Delta T_f = K_f \cdot m \cdot i$ , where $K_f$ is the cryoscopic constant, $m$ is the molality, and $i$ is the van’t Hoff factor.

18. Which of the following is NOT a colligative property?

a) Freezing point depression
b) Osmotic pressure
c) Boiling point elevation
d) Solubility

Answer: d) Solubility
Explanation: Solubility is not a colligative property; it depends on the nature of the solute, unlike colligative properties that depend on the number of solute particles.

19. Which of the following solutions will have the highest boiling point?

a) 0.5 mol NaCl in water
b) 0.5 mol KNO3 in water
c) 0.5 mol glucose in water
d) 0.5 mol H2O in water

Answer: b) 0.5 mol KNO3 in water
Explanation: KNO3 dissociates into three ions (K+, NO3-, and one more ion in the solution), leading to a higher boiling point elevation compared to non-electrolytes.

20. The osmotic pressure of a solution depends on:

a) The temperature
b) The number of solute particles
c) The volume of solution
d) All of the above

Answer: d) All of the above
Explanation: Osmotic pressure depends on temperature, the concentration of solute particles, and the volume of the solution.

21. The van’t Hoff factor for NaCl in water is:

a) 1
b) 2
c) 3
d) 4

Answer: b) 2
Explanation: NaCl dissociates into two ions (Na+ and Cl-) in water, so its van't Hoff factor is 2.

22. If a solution exhibits negative deviations from Raoult’s law, it means that:

a) The intermolecular forces between solute and solvent are weaker than between the solvent molecules
b) The intermolecular forces between solute and solvent are stronger than between the solvent molecules
c) The solute is non-volatile
d) The solution is ideal

Answer: b) The intermolecular forces between solute and solvent are stronger than between the solvent molecules
Explanation: Negative deviations occur when solute-solvent interactions are stronger than solvent-solvent interactions, reducing the vapor pressure.

23. What is the molarity of a solution containing 5 g of NaOH dissolved in 200 mL of solution?

a) 0.5 M
b) 1 M
c) 2.5 M
d) 3 M

Answer: a) 0.5 M
Explanation: Molarity $M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}$ . Moles of NaOH = $\frac{5}{40}$ = 0.125 mol. So, molarity $M = \frac{0.125}{0.2} = 0.5$ .

24. Which of the following will result in the greatest change in freezing point?

a) 1 mol NaCl in 1 kg of water
b) 1 mol K2SO4 in 1 kg of water
c) 1 mol glucose in 1 kg of water
d) 1 mol urea in 1 kg of water

Answer: b) 1 mol K2SO4 in 1 kg of water
Explanation: K2SO4 dissociates into 3 ions (2 K+ and 1 SO4 2-), leading to a higher depression in freezing point than glucose or urea.

25. The molecular weight of a solute can be determined using:

a) Freezing point depression
b) Boiling point elevation
c) Osmotic pressure
d) All of the above

Answer: d) All of the above
Explanation: Freezing point depression, boiling point elevation, and osmotic pressure can all be used to determine the molecular weight of a solute.

26. The vapor pressure of a solution is 30 mm Hg at 25°C. If the vapor pressure of the pure solvent is 40 mm Hg, the mole fraction of the solute in the solution is:

a) 0.25
b) 0.5
c) 0.75
d) 1.0

Answer: a) 0.25
Explanation: Using Raoult's Law, $P = X_{\text{solvent}} P^0_{\text{solvent}}$ . Here, $\frac{P}{P^0} = X_{\text{solvent}}$ . Substituting the given values: $\frac{30}{40} = 0.75$ , so $X_{\text{solute}} = 1 - 0.75 = 0.25$ .

27. What will happen to the osmotic pressure if the temperature of the solution is increased?

a) It will decrease
b) It will increase
c) It will remain constant
d) It will first increase, then decrease

Answer: b) It will increase
Explanation: Osmotic pressure is directly proportional to temperature, so increasing the temperature increases the osmotic pressure.

28. Which of the following statements is true for a solution of a non-volatile solute in a solvent?

a) Vapor pressure of the solution is higher than that of the pure solvent
b) Vapor pressure of the solution is lower than that of the pure solvent
c) The boiling point of the solution is lower than that of the pure solvent
d) The freezing point of the solution is higher than that of the pure solvent

Answer: b) Vapor pressure of the solution is lower than that of the pure solvent
Explanation: The addition of a non-volatile solute to a solvent lowers the vapor pressure of the solvent.

29. The van’t Hoff factor for K2SO4 in water is:

a) 1
b) 2
c) 3
d) 4

Answer: c) 3
Explanation: K2SO4 dissociates into three ions (2 K+ and 1 SO4 2-) in water, so its van't Hoff factor is 3.

30. Which of the following can be used to measure the osmotic pressure of a solution?

a) Barometer
b) Manometer
c) Membrane filter
d) Osmometer

Answer: d) Osmometer
Explanation: An osmometer is an instrument used to measure the osmotic pressure of a solution.

31. The freezing point depression is directly proportional to the molal concentration of the solution. This is a statement of:

a) Raoult’s Law
b) Henry’s Law
c) Beckmann’s Law
d) Cryoscopic Law

Answer: d) Cryoscopic Law
Explanation: The cryoscopic law states that the depression in freezing point is directly proportional to the molal concentration of the solution.

32. If a solution shows positive deviations from Raoult's law, it means:

Answer: a) The intermolecular forces between solute and solvent are weaker than between the solvent molecules
Explanation: Positive deviations occur when solute-solvent interactions are weaker than solvent-solvent interactions, leading to a higher vapor pressure than predicted by Raoult’s Law.

33. Which of the following solutions exhibits the maximum elevation in boiling point?

a) 1 mol NaCl in 1 kg of water
b) 1 mol KNO3 in 1 kg of water
c) 1 mol glucose in 1 kg of water
d) 1 mol urea in 1 kg of water

Answer: b) 1 mol KNO3 in 1 kg of water
Explanation: KNO3 dissociates into three ions, giving the highest number of particles in solution, which leads to the greatest elevation in boiling point.

34. The molality of a solution is related to the freezing point depression by:

a) $\Delta T_f = K_f \cdot m$
b) $\Delta T_f = K_b \cdot m$
c) $\Delta T_f = K_f \cdot i \cdot m$
d) $\Delta T_f = K_f \cdot m \cdot T$

Answer: a) $\Delta T_f = K_f \cdot m$
Explanation: The freezing point depression is proportional to the molality of the solution, as given by the equation $\Delta T_f = K_f \cdot m$ , where $K_f$ is the cryoscopic constant.

35. Which of the following is the correct expression for molarity (M)?

a) $M = \frac{\text{mol of solute}}{\text{liters of solution}}$
b) $M = \frac{\text{mol of solute}}{\text{kg of solvent}}$
c) $M = \frac{\text{mass of solute}}{\text{liters of solution}}$
d) $M = \frac{\text{moles of solute}}{\text{mass of solvent}}$

Answer: a) $M = \frac{\text{mol of solute}}{\text{liters of solution}}$
Explanation: Molarity is defined as the number of moles of solute per liter of solution.

36. The osmotic pressure of a solution is 1.0 atm at 300 K. If the solution's volume is doubled, what will be the osmotic pressure at the new volume?

a) 0.5 atm
b) 1.0 atm
c) 2.0 atm
d) 4.0 atm

Answer: a) 0.5 atm
Explanation: Osmotic pressure is inversely proportional to the volume of the solution. If the volume is doubled, the osmotic pressure will be halved.

37. A solution that contains 0.5 mol of solute in 1 L of solution is said to be:

a) 0.5 molal
b) 0.5 molar
c) 0.5 normal
d) None of the above

Answer: b) 0.5 molar
Explanation: A molar solution contains 1 mole of solute per liter of solution. So, 0.5 moles per liter is a 0.5 molar solution.

38. Which of the following is NOT a characteristic of an ideal solution?

a) The enthalpy of mixing is zero
b) The volume of mixing is zero
c) The solution obeys Raoult’s law at all concentrations
d) The solution exhibits deviations from Raoult's law

Answer: d) The solution exhibits deviations from Raoult's law
Explanation: An ideal solution obeys Raoult’s law at all concentrations and shows no deviations in terms of enthalpy or volume of mixing.

39. The boiling point elevation is directly proportional to:

a) Mole fraction of the solute
b) Molality of the solution
c) Volume of the solution
d) Density of the solution

Answer: b) Molality of the solution
Explanation: Boiling point elevation is directly proportional to the molality of the solution, as given by the equation $\Delta T_b = K_b \cdot m$ .

40. The relationship between vapor pressure and mole fraction of solvent in a solution is given by:

a) Raoult’s Law
b) Henry’s Law
c) Dalton’s Law
d) Gay-Lussac’s Law

Answer: a) Raoult’s Law
Explanation: Raoult's Law relates the vapor pressure of a solvent in a solution to its mole fraction.

41. Which of the following has the highest freezing point depression when 1 mole of each solute is added to 1 kg of water?

a) NaCl
b) KNO3
c) C6H12O6 (glucose)
d) Urea

Answer: b) KNO3
Explanation: KNO3 dissociates into 3 ions (2 K+ and 1 NO3-), resulting in the greatest depression of the freezing point, compared to the others.

42. The molarity of a solution is 2.0 M. What is the number of moles of solute in 500 mL of the solution?

a) 1.0 mol
b) 0.5 mol
c) 2.0 mol
d) 0.1 mol

Answer: b) 0.5 mol
Explanation: Moles of solute = molarity × volume (in liters). So, $2.0 \times 0.5 = 1.0 \, \text{mol}$ .

43. Which of the following will show the largest effect on the osmotic pressure of a solution?

a) Increasing the volume
b) Increasing the temperature
c) Decreasing the volume
d) Decreasing the temperature

Answer: b) Increasing the temperature
Explanation: Osmotic pressure is directly proportional to temperature, so increasing temperature will have the largest effect.

44. The normality of a solution is 1 N. What is the molarity of the solution if the solute is a monoprotic acid?

a) 1.0 M
b) 0.5 M
c) 2.0 M
d) 1.0 N

Answer: a) 1.0 M
Explanation: For monoprotic acids, normality is equal to molarity, so the molarity is also 1.0 M.

45. The solution of which of the following will show negative deviations from Raoult’s law?

a) Water and acetone
b) Water and benzene
c) Water and chloroform
d) Water and ethanol

Answer: c) Water and chloroform
Explanation: Water and chloroform exhibit negative deviations because their intermolecular forces are stronger than the forces between the solvent molecules.

46. Which of the following is the correct relation between freezing point depression and the molality of the solution?

a) $\Delta T_f = K_f \cdot m$
b) $\Delta T_f = K_b \cdot m$
c) $\Delta T_f = K_f \cdot m \cdot T$
d) $\Delta T_f = K_b \cdot m \cdot T$

Answer: a) $\Delta T_f = K_f \cdot m$
Explanation: The depression in freezing point ( $\Delta T_f$ ) is directly proportional to the molality ( $m$ ) of the solution.

47. Which one of the following is true for the solution of NaCl in water?

a) NaCl does not dissociate
b) It shows negative deviations from Raoult's law
c) It does not show any deviation from Raoult's law
d) NaCl dissociates into two ions in water

Answer: d) NaCl dissociates into two ions in water
Explanation: NaCl dissociates into Na+ and Cl- ions in water, which affects the properties of the solution.

48. Which of the following is true for an ideal solution?

a) It follows Raoult’s law over the entire range of concentration
b) It exhibits a positive deviation from Raoult's law
c) It exhibits a negative deviation from Raoult's law
d) The vapor pressure of the solution is always greater than that of the pure solvent

Answer: a) It follows Raoult’s law over the entire range of concentration
Explanation: An ideal solution follows Raoult's law over the entire concentration range.

49. Which of the following does NOT affect the vapor pressure of a solvent in a solution?

a) Nature of the solvent
b) Nature of the solute
c) Temperature
d) Concentration of the solute

Answer: b) Nature of the solute
Explanation: The nature of the solute does not directly affect the vapor pressure of the solvent; it is the concentration of the solute and temperature that affect it.

50. The molar mass of an unknown solute can be determined by: