What volume of hydrogen gas at STP would be liberated by action of $50\text{ mL}$ of $H_2SO_4$ of $50\%$ purity (density $= 1.3\text{ g mL}^{-1}$ ) on $20\text{ g}$ of zinc ?
Given : Molar mass of H, O, S, Zn are $1, 16, 32, 65\text{ g mol}^{-1}$ respectively.

Question

What volume of hydrogen gas at STP would be liberated by action of

50\text{ mL}

of

H_2SO_4

of

50\%

purity (density

= 1.3\text{ g mL}^{-1}

) on

20\text{ g}

of zinc ?
Given : Molar mass of H, O, S, Zn are

1, 16, 32, 65\text{ g mol}^{-1}

respectively.

Quantrex Academy · Accepted Answer

Correct answer: C. 6.892 L

Mass of H_2SO_4 solution = 50 × 1.3 = 65 g Mass of pure H_2SO_4 = 65 × (50)/(100) = 32.5 g Moles of H_2SO_4 = (32.5)/(98) 0.3316 mol Moles of Zn = (20)/(65) 0.3077 mol The balanced chemical equation is: Zn + H_2SO_4 arrow ZnSO_4 + H_2 Since the moles of Zn are less than the moles of H_2SO_4 , Zn is the limiting reagent. Moles of H_2 produced = Moles of Zn = (20)/(65) mol Volume of H_2 gas at STP = (20)/(65) × 22.4 L = 6.892 L Answer: 6.892 L

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