Question

Which of the following sentences is true?

• A. Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute is equal to the mole fraction of the solute at a given temperature
• B. Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute is equal to the mole fraction of the solvent at a given temperature
• C. Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute depends on the nature of the solute at a given temperature
• D. Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute depends on the nature of the solvent at a given temperature

Answer 1

The correct option is A Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute is equal to the mole fraction of the solute at a given temperature

Relative lowering of vapor pressure of an ideal solution containing a non-volatile solute is equal to the mole fraction of the solute at a given temperature.
If $p_A^o$ is the vapor pressure of pure solvent. And $p_A$ is the vapor pressure of the ideal solution after a non-volatile solute is added.
The relative lowering of vapor pressure of the solution becomes $\frac{p_A^o-p_A}{p_A^o}$$=$$X_B$, where $X_B$ is the mole fraction of solute.