30 g of a copper-zinc alloy was treated with a sulfuric acid solution.

30 g of a copper-zinc alloy was treated with a sulfuric acid solution. This released 4.4 liters of hydrogen. Calculate the mass fraction of zinc (%) in this alloy.

Copper does not react with sulfuric acid under normal conditions.

Zinc dissolves in sulfuric acid, the reaction proceeds according to the following chemical equation:

Zn + H2SO4 = ZnSO4 + H2;

Let’s find the molar amount of synthesized hydrogen.

To do this, we divide its volume by the volume of 1 mole of gas (assuming a volume of 22.4 liters).

N H2 = 4.4 / 22.4 = 0.1 mol;

The same amount of zinc will react.

Let’s calculate its mass.

For this purpose, we multiply its weight by the molar weight of elemental zinc.

M Zn = 65 grams / mol;

m Zn = 0.1 x 65 = 6.5 grams;

The mass fraction of zinc in the alloy is 6.5 / 30 = 0.2166 = 21.66%;