When sulfuric acid (excess) acts on a mixture of zinc and copper weighing 19.4 g, hydrogen will be released with a volume of 0.00448 m. Calculate the mass fraction of copper in the mixture.
Copper does not dissolve in hydrochloric acid. Hydrogen is released only when zinc dissolves.
The chemical reaction is described by the following equation:
Zn + 2HCl → ZnCl2 + H2;
To determine the amount of zinc, it is enough to determine the amount of hydrogen.
The amounts of these substances will be the same.
Let’s find the chemical amount of synthesized hydrogen.
N H2 = 0.00448 x 1000 / 22.4 = 0.2 mol;
To obtain such an amount of hydrogen, it is necessary to dissolve 0.2 mol of zinc.
Let’s calculate its weight.
M Zn = 65 grams / mol;
m Zn = 65 x 0.2 = 13 grams;
The mass fraction of copper will be: (19.4 – 13) / 19.4 = 0.33 = 33%
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