In 200 ml of water was dissolved 33.6 l of hydrogen bromide Determine the mass fraction of hydrochloric acid in the solution.

Given:
V (H2O) = 200 ml
V (HBr) = 33.6 l
ρ (H2O) = 1 g / ml
Vm = 22.4 l / mol

Find:
ω (HBr) -?

1) m (H2O) = ρ (H2O) * V (H2O) = 200 * 1 = 200 g;
2) n (HBr) = V (HBr) / Vm = 33.6 / 22.4 = 1.5 mol;
3) M (HBr) = Mr (HBr) = Ar (H) * N (H) + Ar (Br) * N (Br) = 1 * 1 + 80 * 1 = 81 g / mol;
4) m (HBr) = n (HBr) * M (HBr) = 1.5 * 81 = 121.5 g;
5) m solution (HBr) = m (HBr) + m (H2O) = 121.5 + 200 = 321.5 g;
6) ω (HBr) = m (HBr) * 100% / m solution (HBr) = 121.5 * 100% / 321.5 = 37.8%.

Answer: Mass fraction of HBr is 37.8%.