Pyrolusite (MnO2) is dissolved in hydrochloric acid: MnO2 + HCl → MnCl 2 + H2O + Cl 2 The chloride was passed into potassium iodide solution where it liberated iodine: 2 2 Cl + KI → KCl + I The iodine...

Pyrolusite (MnO2) is dissolved in hydrochloric acid:

MnO2 + HCl → MnCl 2 + H2O + Cl 2

The chloride was passed into potassium iodide solution where it liberated iodine:

2 2 Cl + KI → KCl + I

The iodine liberated was estimated by adding sodium thiosulfate, the reaction being

2 Na2 S2O3 NaI Na2 S4O6
I + → +
If 5.6 g of crystallized sodium thiosulfate,
Na2 S2O3
 5H2O
, were used up, how many grams of

manganese were present?

MW (g/mole): I =126.9; Mn =54.94; Cl = 35.45; K = 39.09; Na = 23; S = 32