NEET Solutions — Set 15

Question 1

A 0.25 M solution of a solute in 400 mL of water has an osmotic pressure of 1.845 atm at 27°C. If the solute dissociates into 2 ions, what is the degree of dissociation? ($ R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} $)

Accepted Answer

$ \Pi = i \cdot M \cdot RT $. $ 1.845 = i \times 0.25 \times 0.0821 \times 300 $. $ i = \frac{1.845}{0.25 \times 24.63} \approx 0.3 \times 6 = 1.8 $. $ i = 1 + \alpha $, $ 1.8 = 1 + \alpha $, $ \alpha = 0.8 $.

Question 2

The vapor pressure of pure water at a certain temperature is 50 mm Hg. What is the vapor pressure of a solution with a solute mole fraction of 0.1?

Accepted Answer

Mole fraction of water = $ 1 - 0.1 = 0.9 $. Vapor pressure = $ 50 \times 0.9 = 45 \, \text{mm Hg} $.

Question 3

A 0.25 molal solution of a solute in water has a boiling point elevation of 0.26°C. If the solute dissociates into 2 ions, what is the degree of dissociation? ($ K_b = 0.52 \, \text{K kg mol}^{-1} $)

Accepted Answer

$ \Delta T_b = i \cdot K_b \cdot m $. $ 0.26 = i \times 0.52 \times 0.25 $. $ i = \frac{0.26}{0.52 \times 0.25} = 2 $. $ i = 1 + \alpha (n - 1) $, $ 2 = 1 + \alpha (2 - 1) $, $ \alpha = 1 $.

NEET Chemistry: Solutions — Practice Set 15

Q1. A 0.25 M solution of a solute in 400 mL of water has an osmotic pressure of 1.845 atm at 27°C. If the solute dissociates into 2 ions, what is the degree of dissociation? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q2. The vapor pressure of pure water at a certain temperature is 50 mm Hg. What is the vapor pressure of a solution with a solute mole fraction of 0.1?

Q3. A 0.25 molal solution of a solute in water has a boiling point elevation of 0.26°C. If the solute dissociates into 2 ions, what is the degree of dissociation? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q4. The solubility of a gas in a liquid increases with an increase in:

Q5. The vapor pressure of pure water is 25 mm Hg at a certain temperature. A solution with a non-volatile solute has a vapor pressure of 23 mm Hg. If the solute’s molar mass is 60 g/mol, what is the mass of solute in 180 g of water?

Q6. What is the freezing point depression of a solution containing 18 g of sucrose (molar mass = 342 g/mol) in 400 g of water? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q7. The van’t Hoff factor of a 0.1 m K₂SO₄ solution is 2.4. What is the boiling point elevation? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q8. What is the boiling point elevation of a solution containing 12 g of glucose (molar mass = 180 g/mol) in 600 g of water? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

Q9. What is the osmotic pressure of a 0.025 M solution of a non-electrolyte at 27°C? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q10. A solution contains 23 g of methanol (molar mass = 32 g/mol) and 72 g of water. If 64 g of water is added, what is the new mole fraction of methanol?