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Genrish500
26 days ago
11

Zinc and magnesium metal each reacts with hydrochloric acid to make chloride salts of the respective metals, and hydrogen gas. a

11.20-g mixture of zinc and magnesium produces 0.6854 g of hydrogen gas upon being mixed with an excess of hydrochloric acid. determine the percent magnesium by mass in the original mixture.
Chemistry
1 answer:
Anarel [2.5K]26 days ago
5 0
Total mass = 11.20 g
mass of H₂ = 0.6854 g
molar mass of H₂ = 2.016 g/mol
molar mass of Mg = 24.305 g/mol
molar mass of Zn = 65.39 g/mol
w-?

mass of Mg = wm
mass of Zn = (1-w)m

Zn + 2HCl → ZnCl₂ + H₂
mass of H₂, m₁ = (molar mass of H₂ * mass of Zn) / molar mass of Zn = molar mass of H₂ * (1-w) * m / molar mass of Zn

Mg + 2HCl → MgCl₂ + H₂
mass of H₂, m₂ = (molar mass of H₂ * mass of Mg) / molar mass of Mg = molar mass of H₂ * wm / molar mass of Mg

Total mass of H₂ = m₁ + m₂
mass of H₂ = molar mass of H₂ * (1-w) * m / molar mass of Zn + molar mass of H₂ * wm / molar mass of Mg = molar mass of H₂ * {(1-w)/molar mass of Zn + w/molar mass of Mg}

mass of H₂ = molar mass of H₂ * {(1-w)/molar mass of Zn + w/molar mass of Mg}

{(1-w)/molar mass of Zn + w/molar mass of Mg} = mass of H₂ / (molar mass of H₂ * m)

1/molar mass of Zn - w/molar mass of Zn + w/molar mass of Mg = mass of H₂ / (molar mass of H₂ * m)

w * (1/molar mass of Mg - 1/molar mass of Zn) = mass of H₂ / (molar mass of H₂ * m) - 1/molar mass of Zn

w = [mass of H₂ / (molar mass of H₂ * m) - 1/molar mass of Zn] / (1/molar mass of Mg - 1/molar mass of Zn)

w = 0.583 (58.3%)
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