The mixture of zinc and zinc oxide was treated with excess hydrochloric acid.

The mixture of zinc and zinc oxide was treated with excess hydrochloric acid. The gas evolved was burned and 3.6 g of water was obtained. Calculate the mass of zinc in the mixture.

Let’s compose the equation of the reactions taking place in the mixture.

Zn + 2HCl = ZnCl2 + H2 ↑.

ZnO + 2HCl = ZnCl2 + H2O.

2H2 + O2 = 2H2O.

Let’s find the amount of water substance by the formula:

n = m: M.

M (H2O) = 18 g / mol.

n = 3.6 g: 36 g / mol = 0.1 mol.

Hydrogen is released as a result of the reaction between zinc and hydrochloric acid.

According to the reaction equation for the combustion of hydrogen, 2 mol of hydrogen accounts for 2 mol of water. Substances are in quantitative ratios 1: 1. The amount of substances will be equal.

n (H2O) = n (H2) = 0.1 mol.

According to the reaction equation for the interaction of zinc and hydrochloric acid, 1 mole of hydrogen accounts for 1 mole of zinc.

The amount of substance will be equal.

n (Zn) = n (H2) = 0.1 mol.

Let’s find the mass of zinc.

m = n × M.

M (Zn) = 65 g / mol.

m = 65 g / mol × 0.1 mol = 6.5 g.

Answer: 6.5 g.