Determine the mass and volume of hydrogen, which is formed as a result of the interaction of 40 g

Determine the mass and volume of hydrogen, which is formed as a result of the interaction of 40 g of Zn, containing 20% impurities, and hydrochloric acid.

Given:

m (Zn) = 40 g.

m (H2) -?

V (gas) -?

Solution:

Let’s find the mass of zinc without impurities.

100% – 20% = 80%.

40 g – 100%,

m – 80%,

m = (40 g × 80%): 100% = 32 g.

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

n = m: M.

M (Zn) = 65 g / mol.

n = 32 g: 65 g / mol = 0.49 mol.

Let’s compose the reaction equation. Let us find in what quantitative ratios the substances are.

Zn + 2HCl = ZnCl2 + H2 ↑.

1 mole of zinc accounts for 1 mole of hydrogen.

The substances are in quantitative ratios of 1: 1.

Therefore, their amount of substance will be equal.

Let’s find the mass of hydrogen.

M (H2) = 2 g / mol.

m = n × M,

m = 0.49 mol × 2 g / mol = 0.98 g.

Let’s find the volume of hydrogen.

V = Vn n, where Vn is the molar volume of gas, equal to 22.4 l / mol, and n is the amount of substance.

V = 0.49 L × 22.4 L / mol = 10.98 L = 11 L.

Answer: m = 0.98 g; V = 11 liters.