What volume of hydrogen gas at STP would be liberated by action of 50 mL of H2SO4 of 50% purity (density = 1.3 g mL-1) on 20 g of zinc? Given : Molar mass of H, O, S, Zn are 1, 16, 32, 65 g mol-1 respectively.
- 5.824 L
- 7.428 L
- 6.892 L
- 8.375 L
Answer
(3) 6.892 L
Solution
Zn + H2SO4 ZnSO4 + H2 (1 : 1 : 1)
Mass of acid solution = 50 mL × 1.3 g mL-1 = 65 g
⇒ mass of pure H2SO4 = 65 × 50100 = 32.5 g
⇒ moles of H2SO4 = 32.598 = 0.332 mol
Moles of Zn = 2065 = 0.3077 mol
∵ 0.3077 < 0.332 ⇒ Zn is the limiting reagent
∴ moles of H2 = moles of Zn = 0.3077 mol
⇒ volume of H2 at STP = 0.3077 × 22.4 L = 6.892 L
Answer: (3)