When zinc, containing 9.5% of insoluble impurities, was dissolved in an excess of dilute sulfuric acid, 4.48 liters of hydrogen were released. Determine the mass of the original metal sample containing impurities.
1) Let’s compose the reaction equation:
Zn + H2SO4 = ZnSO4 + H2 ↑
2) Calculate the amount of hydrogen and zinc substance:
n (H2) = V (H2) / Vm = 4.48 / 22.4 = 0.2 mol
according to the reaction equation
n (Zn) = n (H2) = 0.2 mol;
3) Determine the mass, mass fraction of pure zinc and the mass of the mixture (the original sample containing impurities):
m (Zn) = n (Zn) ∙ M (Zn) = 0.2 ∙ 65 = 13 g.
ω (Zn) = 100 – ω (impurities) = 100-9.5 = 90.5%
m (mixture) = (m (Zn) ∙ 100) / ω (Zn) = 13 ∙ 100 / 90.5 = 14.36 g.
Answer: 14.36 g.
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