JEE Main 2025 Apr 3 Shift 2, Chemistry Q12: Mole Concept And Equivalent Concept

JEE Main2025Apr 3, Shift 2Chemistry

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 g mol $^{- 1}$ .

Solution

Balanced reaction: Mg + 2 HCl $\to$ MgCl $_{2}$ + H $_{2}$ . One mole of Mg releases one mole of H $_{2}$ .

Moles of H $_{2}$ at STP (22.4 L mol $^{- 1}$ ) $= \frac{0.220}{22.4} \approx 9.82 \times 1 0^{- 3}$ mol.

So moles of Mg required $\approx 9.82 \times 1 0^{- 3}$ mol.

Mass of Mg $= 9.82 \times 1 0^{- 3} \times 24 \approx 0.2357$ g $= 235.7$ mg $\approx 236$ mg.

$∴$ Option (3), 236 mg, is correct.

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