NEET Solutions — Set 5

Question 1

How many moles of NaOH are present in 500 mL of a 0.2 M solution?

Accepted Answer

Molarity = $ \frac{\text{Moles of solute}}{\text{Volume in liters}} $. Moles = Molarity × Volume = $ 0.2 \, \text{mol/L} \times 0.5 \, \text{L} = 0.1 \, \text{mol} $.

Question 2

The partial pressure of a gas above a solution is 2 bar, and its Henry’s law constant is 100 bar. What is the mole fraction of the gas in the solution?

Accepted Answer

Henry’s law: $ p = K_H \cdot x $. $ x = \frac{p}{K_H} = \frac{2}{100} = 0.02 $.

Question 3

The molar mass of a solute is 100 g/mol if 10 g of it in 1 L of solution produces an osmotic pressure of 0.246 atm at 27°C. ($ R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} $)

Accepted Answer

$ \Pi = \frac{w}{M V} RT $. $ 0.246 = \frac{10}{M \times 1} \times 0.0821 \times 300 $. $ M = \frac{10 \times 0.0821 \times 300}{0.246} \approx 100 \, \text{g/mol} $.

NEET Chemistry: Solutions — Practice Set 5

Q1. How many moles of NaOH are present in 500 mL of a 0.2 M solution?

Q2. The partial pressure of a gas above a solution is 2 bar, and its Henry’s law constant is 100 bar. What is the mole fraction of the gas in the solution?

Q3. The molar mass of a solute is 100 g/mol if 10 g of it in 1 L of solution produces an osmotic pressure of 0.246 atm at 27°C. (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

Q4. A 0.1 molal NaCl solution has a van’t Hoff factor of 1.8. What is the freezing point depression? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q5. A solution is made by dissolving 20 g of a solute in 80 g of water. If the mass percentage of the solute is doubled in a new solution with the same solute mass, what is the mass of water required?

Q6. A solution of two volatile liquids has vapor pressures of 150 mm Hg and 250 mm Hg for pure components. If the total vapor pressure is 190 mm Hg, what is the mole fraction of the first component?

Q7. A solution of two volatile liquids has vapor pressures of 200 mm Hg and 300 mm Hg for pure components. If the total vapor pressure is 260 mm Hg, what is the mole fraction of the first component?

Q8. A solution of a non-volatile solute in water has a vapor pressure of 23.7 mm Hg at a temperature where pure water’s vapor pressure is 25 mm Hg. If the solution freezes at -0.372°C, what is the molality? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

Q9. A solution of two volatile liquids has vapor pressures of 300 mm Hg and 400 mm Hg for pure components. If the mole fraction of the second component in the vapor phase is 0.6, what is the total vapor pressure?

Q10. The vapor pressure of pure water is 24 mm Hg at a certain temperature. What is the vapor pressure of a solution with a solute mole fraction of 0.25?