0.01 mole of an organic compound $(X)$ containing $10 \%$ hydrogen, on complete combustion produced $0.9…

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 $(\mathrm{X})$ is _____ $\mathrm{g} \mathrm{mol}^{-1}$.

Solution

Organic compound $\xrightarrow{\text { combustion }} \underset{\substack{\mathrm{0.9} \mathrm{gm}}}{\mathrm{H}_2 \mathrm{O}}$
$\therefore$ mole of $\mathrm{H}_2 \mathrm{O}=\frac{0.9}{18}=0.05 \mathrm{~mole}$
$\therefore$ mole of H in $\mathrm{H}_2 \mathrm{O}=0.05 \times 2=0.1$ mole
$=$ mole of H in 0.01 mole
Organic compound
$\therefore$ wt of H atom in 0.01 mole compound $=0.1 \times 1$ $=0.1 \mathrm{gm}$
$\therefore$ wt of H atom in one mole compound
$=\frac{0.1}{0.01}=10 \mathrm{gm}$
$\because \mathrm{wt}. \%$ of $\mathrm{H}=\frac{\mathrm{wt} \text {. of } \mathrm{H} \text { in one mole compound }}{\text { Molar mass of compound }} \times 1$
$\begin{aligned}
& 10=\frac{10}{M} \times 100 \\
& \therefore M=100
\end{aligned}$

Asked in: JEE Main 2025 (23 Jan Shift 2)

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