NEET Solutions — Set 19

Question 1

What is the mass percentage of a solution prepared by dissolving 15 g of a solute in 85 g of water?

Accepted Answer

Total mass = $ 15 + 85 = 100 \, \text{g} $. Mass % = $ \frac{15}{100} \times 100 = 15\% $.

Question 2

What is the boiling point elevation of a solution containing 10 g of fructose (molar mass = 180 g/mol) in 400 g of water? ($ K_b = 0.52 \, \text{K kg mol}^{-1} $)

Accepted Answer

Moles of fructose = $ \frac{10}{180} \approx 0.0556 \, \text{mol} $. Molality = $ \frac{0.0556}{0.4} \approx 0.139 \, \text{mol/kg} $. $ \Delta T_b = 0.52 \times 0.139 \approx 0.0723 \, \text{K} $.

Question 3

What is the mass of ethanol (molar mass = 46 g/mol) in 500 g of a solution if its mole fraction is 0.2 and water is the solvent?

Accepted Answer

Moles of water = $ \frac{500 - x}{18} $, moles of ethanol = $ \frac{x}{46} $. Mole fraction = $ \frac{\frac{x}{46}}{\frac{x}{46} + \frac{500 - x}{18}} = 0.2 $. Solving: $ \frac{x}{46} = 0.2 \left( \frac{x}{46} + \frac{500 - x}{18} \right) $. Simplify: $ x \approx 138 \, \text{g} $ (after cross-multiplication and approximation).

NEET Chemistry: Solutions — Practice Set 19

Q1. What is the mass percentage of a solution prepared by dissolving 15 g of a solute in 85 g of water?

Q2. What is the boiling point elevation of a solution containing 10 g of fructose (molar mass = 180 g/mol) in 400 g of water? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q3. What is the mass of ethanol (molar mass = 46 g/mol) in 500 g of a solution if its mole fraction is 0.2 and water is the solvent?

Q4. The vapor pressure of pure water is 25 mm Hg at a certain temperature. What is the vapor pressure of a solution containing 0.1 mole of a non-volatile solute in 0.9 mole of water?

Q5. What is the mole fraction of a solute if its solution lowers the vapor pressure of water from 25 mm Hg to 24 mm Hg?

Q6. A gas has a Henry’s law constant of 300 bar. If its partial pressure is 6 bar, what is the mole fraction in the solution?

Q7. A solution containing 0.1 mole of a non-volatile solute in 1 kg of water has an osmotic pressure of 2.46 atm at 27°C. What is the van’t Hoff factor? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \), assume 1 L solution)

Q8. What is the molality of a solution containing 14 g of ethylene glycol (molar mass = 62 g/mol) in 350 g of water?

Q9. A 0.2 molal Na₂SO₄ solution has a van’t Hoff factor of 2.5. What is the freezing point depression? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q10. A gas has a partial pressure of 5 bar and a Henry’s law constant of 500 bar. What is the mole fraction in the solution?