0.01 mole of an organic compound (X) containing $10\%$ hydrogen, on complete combustion produced $0.9 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}$. Molar mass of (X) is ______ $\mathrm{g} \mathrm{mol}^{-1}$.

JEE Main · 2025 · 23 Jan 2025 · Shift 2 · Some Basic Concepts of Chemistry

0.01 mole of an organic compound (X) containing

10%

hydrogen, on complete combustion produced

0.9 g H_{2} O

. Molar mass of (X) is ______

g mol^{- 1}

Answer: 100

Combustion of 0.01 mol of X gives 0.9 g of

H X_{2} O

, i.e.

0.9/18 = 0.05

mol

H X_{2} O

, containing

0.05 \times 2 = 0.1

mol of H atoms (0.1 g), coming from 0.01 mol of X. One mole of X therefore contains

0.1/0.01 = 10

g of hydrogen. Since hydrogen is 10% of the molar mass by mass,

10 = \frac{10}{M} \times 100

, giving

M = 100 g mo l^{- 1}

JEE Main · 2025 · 23 Jan 2025 · Shift 2 · Integer answer