Today chlorine is prepared from sodium chloride by electrochemical decomposition. Formerly chlorine was produced by heating hydrochloric acid with pyrolusite (manganese (IV) oxide, MnO2), a common manganese ore. Small amounts of chlorine may be prepared in the laboratory by the same reaction: 4HCl (aq) + MnO2 (s) → 2H2O (l) + MnCl2 (aq) + Cl2 (g) How many grams of HCl react with 5.18 g of manganese dioxide, according to this equation?

Answer: 8.702g of HCl

Explanation:

Using the details from the equation;

4HCl (aq) + MnO2 (s) → 2H2O (l) + MnCl2 (aq) + Cl2 (g)

The molecular mass of HCl is; 4 (1 + 35.5) = 146g

The molecular mass of MnO2 is; (54.9 + 32) = 86.9g

From the equation it means;

86.9g of MnO2 reacts with 146g of HCl

if 1 g of MnO2 reacts with 146 : 86.9 of HCl

∴ 5.18g of MnO2 will react with; 146 : 86.9 x 5.18 = 8.702g of HCl

Note: Approximations were made during the determination of the molecular masses.