NEET Solutions — Set 10

Question 1

What is the molality of a solution containing 10 g of glycerol (molar mass = 92 g/mol) in 200 g of water?

Accepted Answer

Moles of glycerol = $ \frac{10}{92} \approx 0.1087 \, \text{mol} $. Mass of solvent = 200 g = 0.2 kg. Molality = $ \frac{0.1087}{0.2} \approx 0.5435 \, \text{mol/kg} $.

Question 2

The osmotic pressure of a 0.01 M solution at 27°C is: ($ R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} $)

Accepted Answer

$ \Pi = MRT $. $ \Pi = 0.01 \times 0.0821 \times 300 \approx 0.246 \, \text{atm} $.

Question 3

The van’t Hoff factor of a 0.06 m K₂SO₄ solution is 2.5. What is the boiling point elevation? ($ K_b = 0.52 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_b = i \cdot K_b \cdot m $. $ \Delta T_b = 2.5 \times 0.52 \times 0.06 = 0.078 \, \text{K} $.

NEET Chemistry: Solutions — Practice Set 10

Q1. What is the molality of a solution containing 10 g of glycerol (molar mass = 92 g/mol) in 200 g of water?

Q2. The osmotic pressure of a 0.01 M solution at 27°C is: (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q3. The van’t Hoff factor of a 0.06 m K₂SO₄ solution is 2.5. What is the boiling point elevation? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q4. What is the mole fraction of a solute if the vapor pressure of a solution is 27 mm Hg and that of pure solvent is 30 mm Hg?

Q5. A solution of a gas in water has a mole fraction of 0.02 at 5 bar pressure. If the Henry’s law constant decreases by 20% due to a temperature change, what is the new partial pressure?

Q6. A 0.15 molal solution of CaCl₂ in water has a freezing point depression of 0.837°C. What is the van’t Hoff factor? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q7. A solution boils at 100.26°C at 1 atm. What is the molality if \( K_b = 0.52 \, \text{K kg mol}^{-1} \)?

Q8. A solution of two volatile liquids has vapor pressures of 250 mm Hg and 350 mm Hg for pure components. If the mole fraction of the first is 0.6, what is the total vapor pressure?

Q9. A solution of a non-volatile solute in water has a vapor pressure of 23.5 mm Hg at a temperature where pure water’s vapor pressure is 25 mm Hg. If the solution’s boiling point is 100.26°C at 1 atm, what is the molality? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q10. A solution of a non-volatile solute reduces the vapor pressure of a solvent from 30 mm Hg to 27 mm Hg. What is the mole fraction of the solvent?