What mass of a 20% hydrochloric acid solution is required to completely dissolve 20 g of a mixture of zinc and zinc oxide, if 4.48 liters of hydrogen are released?
Metallic zinc enters into a violent reaction with hydrochloric acid with the release of hydrogen gas and the formation of zinc chloride:
Zn + 2HCl = ZnCl2 + H2;
1 mole of metal reacts with 2 moles of acid. This synthesizes 1 mol of salt and 1 mol of hydrogen.
Let’s calculate the released amount of hydrogen. To do this, we divide the volume of synthesized hydrogen by the volume of 1 mole of gas, which is 22.4 liters.
V H2 = 4.48 liters; N H2 = 4.48 / 22.4 = 0.2 mol;
To synthesize such an amount of hydrogen, it is necessary to take twice the amount of hydrogen chloride. Let’s calculate its weight.
N HCl = 0.4 mol;
M HCl = 1 + 35.5 = 36.5 grams / mol; m HCl = 0.4 x 36.5 = 14.6 grams;
The weight of a 20% acid solution will be 14.6 / 0.2 = 73 grams.
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