Q21 / 75 · JEE Main 2025 (3 Apr Shift 2) · Chemistry
Mass of magnesium required to produce 220 mL of hydrogen gas at STP on reaction with excess of dil. HCl is
Given : Molar mass of Mg is $24 \mathrm{~g} \mathrm{~mol}^{-1}$.
Given : Molar mass of Mg is $24 \mathrm{~g} \mathrm{~mol}^{-1}$.
- A235.7 g
- B0.24 mg
- Correct answerC236 mg
- D2.444 g
Solution
$\mathrm{Mg}+2 \mathrm{HCl} \rightarrow \mathrm{MgCl}_2+\mathrm{H}_2$
Volume $\mathrm{H}_2$ evolved $=220 \mathrm{ml}$
Mole of $\mathrm{H}_2=\frac{220 \times 10^{-3}}{22.4}=$ mole of Mg used
$\begin{aligned}<br />\therefore \text { Mass of Mg used } & =\frac{220 \times 10^{-3}}{22.4} \times 24 \\<br>& =235.7 \times 10^{-3} \mathrm{gm} \\<br>& =235.7 \mathrm{mg}<br />\end{aligned}$
Volume $\mathrm{H}_2$ evolved $=220 \mathrm{ml}$
Mole of $\mathrm{H}_2=\frac{220 \times 10^{-3}}{22.4}=$ mole of Mg used
$\begin{aligned}<br />\therefore \text { Mass of Mg used } & =\frac{220 \times 10^{-3}}{22.4} \times 24 \\<br>& =235.7 \times 10^{-3} \mathrm{gm} \\<br>& =235.7 \mathrm{mg}<br />\end{aligned}$
Hence, the correct answer is option: 'C'.