Question

0.5g of non-volatile solute is added to 39g of Benzene. Then vapor pressure of solution is (vapor pressure of pure Benzene is 0.850 torr)

• A. 0.845 torr
• B. 0.850 torr
• C. 0.860 torr
• D. 0.870 torr

Hint:

When calculating vapor pressure depression, use Raoult's Law and remember to consider the molar masses and the mass of the solute and solvent.

Answer 1

The Correct Option is A

The change in vapor pressure due to the addition of a non-volatile solute can be calculated using Raoult's Law:
\[ \Delta P = P_0 - P = \frac{n_{\text{solute}}}{n_{\text{solvent}}} \times P_0 \] Given that \( P_0 = 0.850 \) torr and the amount of solute added is small, the new vapor pressure is:
\[ \text{New vapor pressure} = 0.845 \, \text{torr} \]