6.62 L of hydrogen chloride was dissolved in 100 g of water. Calculate the mass fraction of HCl (%) in this solution.

Given:
m (H2O) = 100 g
V (HCl) = 6.62 L

To find:
ω (HCl) -?

1) n (HCl) = V / Vm = 6.62 / 22.4 = 0.296 mol;
2) m (HCl) = n * M = 0.296 * 36.5 = 10.804 g;
3) m solution (HCl) = m (H2O) + m (HCl) = 100 + 10.804 = 110.804 g;
4) ω (HCl) = m * 100% / m solution = 10.804 * 100% / 110.804 = 9.75%.

Answer: Mass fraction of HCl is 9.75%.