NEET Solutions — Set 4

Question 1

What is the osmotic pressure of a 0.03 M solution of a non-electrolyte at 27°C? ($ R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} $)

Accepted Answer

$ \Pi = MRT $. $ \Pi = 0.03 \times 0.0821 \times 300 \approx 0.7383 \, \text{atm} $.

Question 2

A solution contains 10% by mass of a solute in water. If 50 g of this solution is taken, what is the mass of the solute?

Accepted Answer

Mass of solute = $ \frac{10}{100} \times 50 = 5 \, \text{g} $.

Question 3

A solution of a non-volatile solute in water has a vapor pressure of 22.4 mm Hg at a temperature where pure water’s vapor pressure is 24 mm Hg. If the solution boils at 100.208°C at 1 atm, what is the molality? ($ K_b = 0.52 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_b = 100.208 - 100 = 0.208 \, \text{K} $. $ \Delta T_b = K_b \cdot m $. $ 0.208 = 0.52 \cdot m $, $ m = \frac{0.208}{0.52} = 0.4 \, \text{mol/kg} $. Cross-check: $ x_{\text{solute}} = \frac{24 - 22.4}{24} = 0.0667 $, consistent for dilute solution.

NEET Chemistry: Solutions — Practice Set 4

Q1. What is the osmotic pressure of a 0.03 M solution of a non-electrolyte at 27°C? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q2. A solution contains 10% by mass of a solute in water. If 50 g of this solution is taken, what is the mass of the solute?

Q3. A solution of a non-volatile solute in water has a vapor pressure of 22.4 mm Hg at a temperature where pure water’s vapor pressure is 24 mm Hg. If the solution boils at 100.208°C at 1 atm, what is the molality? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q4. A solution of a non-volatile solute in water boils at 100.78°C at 1 atm. If 10 g of the solute (molar mass = 50 g/mol) was used in 500 g of water, what is the van’t Hoff factor? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q5. A solution lowers the vapor pressure of a solvent from 32 mm Hg to 30 mm Hg. What is the mole fraction of the solute?

Q6. What is the freezing point depression of a solution containing 8 g of urea (molar mass = 60 g/mol) in 200 g of water? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q7. A solution is made by dissolving a non-volatile solute in 900 g of water. If the freezing point decreases by 0.93°C and \( K_f = 1.86 \, \text{K kg mol}^{-1} \), what is the molality of the solution?

Q8. A solution freezes at -0.372°C. What is the molality of the solution if \( K_f = 1.86 \, \text{K kg mol}^{-1} \)?

Q9. A solution of 0.02 mole of a non-volatile solute in 250 mL of water has an osmotic pressure of 0.984 atm at 27°C. What is the molarity of the solution? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q10. A gas dissolves in a liquid with a partial pressure of 1.5 bar and a Henry’s law constant of 75 bar. What is the mole fraction of the gas?