NEET Solutions — Set 9

Question 1

A 0.5 M solution of K₂SO₄ (molar mass = 174 g/mol) has a density of 1.15 g/mL. What is the mass of the solute in 300 mL of this solution?

Accepted Answer

Moles = $ 0.5 \times 0.3 = 0.15 \, \text{mol} $. Mass of K₂SO₄ = $ 0.15 \times 174 = 26.1 \, \text{g} $. (Density is extra info, not needed for molarity-based calculation.)

Question 2

A solution lowers the vapor pressure of a solvent from 40 mm Hg to 38 mm Hg. What is the mole fraction of the solute?

Accepted Answer

$ \frac{p^0 - p}{p^0} = x_{\text{solute}} $. $ \frac{40 - 38}{40} = \frac{2}{40} = 0.05 $.

Question 3

The solubility of a gas in a solvent follows Henry’s law with a constant of 180 bar. If the partial pressure is increased by 50% from 6 bar, what is the new mole fraction of the gas?

Accepted Answer

Initial $ p = 6 \, \text{bar} $, new $ p = 6 \times 1.5 = 9 \, \text{bar} $. $ p = K_H \cdot x $. New $ x = \frac{9}{180} = 0.05 $.

NEET Chemistry: Solutions — Practice Set 9

Q1. A 0.5 M solution of K₂SO₄ (molar mass = 174 g/mol) has a density of 1.15 g/mL. What is the mass of the solute in 300 mL of this solution?

Q2. A solution lowers the vapor pressure of a solvent from 40 mm Hg to 38 mm Hg. What is the mole fraction of the solute?

Q3. The solubility of a gas in a solvent follows Henry’s law with a constant of 180 bar. If the partial pressure is increased by 50% from 6 bar, what is the new mole fraction of the gas?

Q4. What is the molar mass of a solute if 3 g of it in 200 mL of solution produces an osmotic pressure of 0.738 atm at 27°C? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q5. A 0.1 M solution of K₃PO₄ (assuming complete dissociation) has an osmotic pressure of 0.984 atm at a certain temperature. What is the temperature? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q6. A solution of 18 g of glucose (molar mass = 180 g/mol) in 1 kg of water freezes at -0.186°C. What is the \( K_f \) of water?

Q7. A 0.3 M solution of Na₂SO₄ (assuming complete dissociation) has an osmotic pressure of 2.214 atm at a certain temperature. What is the temperature? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q8. A solute dissociates into 3 ions with a van’t Hoff factor of 2.4. What is the degree of dissociation?

Q9. A solution reduces the vapor pressure of a solvent from 28 mm Hg to 26 mm Hg. What is the mole fraction of the solute?

Q10. The vapor pressure of pure water is 30 mm Hg at a certain temperature. A solution with a non-volatile solute has a vapor pressure of 28.5 mm Hg. If the solute’s molality is 0.5 mol/kg, what is the mass of water in the solution?