Question

Assertion :Relative lowering of vapour pressure is equal to the mole fraction of the solvent
Reason: Relative lowering of vapour pressure is a colligative property

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is incorrect but Reason is correct
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is C Assertion is incorrect but Reason is correct

Relative lowering of vapor pressure:

The vapor pressure of a liquid is the pressure of the vapor which is in equilibrium with that liquid. The vapor pressure of a solvent is lowered when a non-volatile solute is dissolved in it to form a solution.The reduction of vapor pressure of solvent is given as

$p_1=x.{p_1}^0$

$p_1$ is vapor pressure of the solution.

${p_1}^0$ is the vapor pressure of pure solvent

$x$ is the mole fraction of solute

Relative lowering of vapor pressure is $p_1$/${p_1}^0=x$

Where x is mole fraction of solute and not solvent. Statement 1 is false.

Relative lowering of vapor pressure is a colligative property.