$10\text{ g}$ of a non-volatile solute is dissolved in $200\text{ g}$ of water to make a solution. It has a vapour pressure of $31\cdot84\text{ mm Hg}$ at $308\text{ K}$. Calculate the molar mass of the solute. [Given : Vapour pressure of pure water at $308\text{ K} = 32\text{ mm Hg}$]

Year	Paper Code	Set	Position
CBSE 2026	Series 56-7	Set 1	Question 20
CBSE 2026	Series 56-7	Set 2	Question 17
CBSE 2026	Series 56-7	Set 3	Question 20

• Step 1: Stating the fundamental formula / law statement (+1 Mark)
• Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
• Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)