NEET Solutions — Set 1

Question 1

What is the mole fraction of water in a solution containing 18 g of water and 46 g of ethanol (molar mass of ethanol = 46 g/mol)?

Accepted Answer

Moles of water = $ \frac{18}{18} = 1 \, \text{mol} $. Moles of ethanol = $ \frac{46}{46} = 1 \, \text{mol} $. Total moles = 1 + 1 = 2. Mole fraction of water = $ \frac{1}{2} = 0.5 $.

Question 2

What is the freezing point depression of a solution containing 9 g of glucose (molar mass = 180 g/mol) in 250 g of water? ($ K_f = 1.86 \, \text{K kg mol}^{-1} $)

Accepted Answer

Moles of glucose = $ \frac{9}{180} = 0.05 \, \text{mol} $. Molality = $ \frac{0.05}{0.25} = 0.2 \, \text{mol/kg} $. $ \Delta T_f = 1.86 \times 0.2 = 0.372 \, \text{K} $.

Question 3

A solution of a non-volatile solute in 600 g of water freezes at -0.62°C. If the solute’s molar mass is 62 g/mol, what is the mass of the solute? ($ K_f = 1.86 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_f = K_f \cdot m $. $ 0.62 = 1.86 \times \frac{\text{moles}}{0.6} $. Moles = $ \frac{0.62 \times 0.6}{1.86} \approx 0.2 $. Mass = $ 0.2 \times 62 = 12.4 \, \text{g} $.

NEET Chemistry: Solutions — Practice Set 1

Q1. What is the mole fraction of water in a solution containing 18 g of water and 46 g of ethanol (molar mass of ethanol = 46 g/mol)?

Q2. What is the freezing point depression of a solution containing 9 g of glucose (molar mass = 180 g/mol) in 250 g of water? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q3. A solution of a non-volatile solute in 600 g of water freezes at -0.62°C. If the solute’s molar mass is 62 g/mol, what is the mass of the solute? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q4. What is the mass percentage of a solution if 25 g of a solute is dissolved in 225 g of water?

Q5. A 0.15 molal solution of a solute in water has a freezing point depression of 0.558°C. If the solute dissociates into 2 ions, what is the degree of dissociation? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q6. A solution freezes at -0.558°C. What is the molality if \( K_f = 1.86 \, \text{K kg mol}^{-1} \)?

Q7. A gas follows Henry’s law with a constant of 200 bar. If its solubility in a solvent is 0.015 mol/kg at 3 bar, what is the mass of solvent required to dissolve 0.03 mole of the gas at the same pressure?

Q8. What is the molality of a solution containing 12 g of sucrose (molar mass = 342 g/mol) in 300 g of water?

Q9. What is the molality of a solution prepared by dissolving 15 g of urea (molar mass = 60 g/mol) in 250 g of water?

Q10. The van’t Hoff factor of a 0.08 m CaCl₂ solution is 2.6. What is the boiling point elevation? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))