Organic compound combustion 0.9gmH2O ∴ mole of H2O=180.9=0.05 mole ∴ mole of H in H2O=0.05×2=0.1 mole = mole of H in 0.01 mole Organic compound ∴ wt of H atom in 0.01 mole compound =0.1×1 =0.1gm ∴ wt of H atom in one mole compound =0.010.1=10gm ∵wt.% of H= Molar mass of compound wt. of H in one mole compound ×1 $\begin{aligned}
& 10=\frac{10}{M} \times 100 \
& \therefore M=100
\end{aligned}$