JEE Main 2025 — Some Basic Concepts Of Chemistry Question with Solution

Organic compound $\stackrel{\text{ combustion }}{\to }\underset{\begin{array}{c}0.9\mathrm{gm}\end{array}}{{\mathrm{H}}_2\mathrm{O}}$

$$\begin{array}{rl}& \therefore \text{ mole of }{\mathrm{H}}_2\mathrm{O}=\frac{0.9}{18}=0.05\text{ mole }\\ & \begin{array}{rl}\therefore \text{ mole of }\mathrm{H}\text{ in }{\mathrm{H}}_2\mathrm{O}& =0.05\times 2=0.1\text{ mole }\\ & =\text{ mole of }\mathrm{H}\text{ in }0.01\text{ mole }\\ & \text{ Organic compound }\end{array}\end{array}$$

$$\begin{array}{rl}& \begin{array}{rl}\therefore \text{ wt of }\mathrm{H}\text{ atom in }0.01\text{ mole compound }& =0.1\times 1\\ & =0.1\mathrm{gm}\end{array}\\ & \therefore \text{ wt of }\mathrm{H}\text{ atom in one mole compound }\\ & \begin{array}{rl}& =\frac{0.1}{0.01}=10\mathrm{gm}\\ & \because \text{ wt. }\%\text{ of }H=\frac{\text{ wt. of }H\text{ in one mole compound }}{\text{ Molar mass of compound }}\times 1\\ & 10=\frac{10}{M}\times 100\\ & \therefore M=100\end{array}\end{array}$$