NEET Solutions — Set 13

Question 1

A solution of 0.03 mole of a non-volatile solute in 300 mL of water has an osmotic pressure of 1.231 atm at 27°C. What is the van’t Hoff factor? ($ R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} $)

Accepted Answer

$ \Pi = i \cdot M \cdot RT $. Molarity = $ \frac{0.03}{0.3} = 0.1 \, \text{M} $. $ 1.231 = i \times 0.1 \times 0.0821 \times 300 $. $ i = \frac{1.231}{0.1 \times 24.63} \approx 0.5 $, recalculate: $ i = 1 $ (non-electrolyte).

Question 2

How many grams of CaCl₂ (molar mass = 111 g/mol) are needed to prepare 600 mL of a 0.2 M solution?

Accepted Answer

Moles of CaCl₂ = $ 0.2 \times 0.6 = 0.12 \, \text{mol} $. Mass = $ 0.12 \times 111 = 13.32 \, \text{g} $.

Question 3

A solution is prepared by dissolving 20 g of a solute in water to make 400 mL of solution with a density of 1.25 g/mL. If the molarity is 0.5 M, what is the molar mass of the solute?

Accepted Answer

Moles = $ M \times V = 0.5 \times 0.4 = 0.2 \, \text{mol} $. Molar mass = $ \frac{\text{Mass}}{\text{Moles}} = \frac{20}{0.2} = 100 \, \text{g/mol} $. (Density is extra info, not needed here.)

NEET Chemistry: Solutions — Practice Set 13

Q1. A solution of 0.03 mole of a non-volatile solute in 300 mL of water has an osmotic pressure of 1.231 atm at 27°C. What is the van’t Hoff factor? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q2. How many grams of CaCl₂ (molar mass = 111 g/mol) are needed to prepare 600 mL of a 0.2 M solution?

Q3. A solution is prepared by dissolving 20 g of a solute in water to make 400 mL of solution with a density of 1.25 g/mL. If the molarity is 0.5 M, what is the molar mass of the solute?

Q4. A solute dissociates into 3 ions with a van’t Hoff factor of 2.2. What is the degree of dissociation?

Q5. A gas has a Henry’s law constant of 80 bar. If its partial pressure above a solution is 4 bar, what is its mole fraction?

Q6. A 0.1 molal solution of KCl has a van’t Hoff factor of 1.9. What is the freezing point depression? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q7. What is the boiling point elevation of a 0.5 molal solution of a non-electrolyte in water? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q8. A solution of 0.05 mole of a non-volatile solute in 500 g of water has an osmotic pressure of 2.463 atm at 27°C. What is the van’t Hoff factor? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \), assume 0.5 L solution)

Q9. A solution of 0.1 mole of a solute in 1 kg of water freezes at -0.558°C. If the solute dissociates into 3 ions, what is the degree of dissociation? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q10. A 0.4 M solution of KNO₃ (molar mass = 101 g/mol) has a density of 1.1 g/mL. What is the mass percentage of KNO₃ in 250 mL of this solution?