Question

4.35 g of a sample of pyrolusite when heated with conc. HCl gave chlorine. The chlorine then passed through KI solution liberated 6.35 g of iodine . Then% purity of the pyrolusite sample is?

Answer 1

Pyrolusite is compound with formula MnO2.

It can react with HCl with chlorine producing:

MnO2 + 4HCl --> MnCL2 + CL2 +2H2O.

The reaction of Cl2 with Ki is next:

Cl2 +2KI=2KCl + I2

Using this equations it is possible to find mass of MnO2

& m 6.35
Cl2 +2KI=2KCl + I2
& 76 254

m=1.9 g


& m & 1.9
MnO2 + 4HCl --> MnCL2 + CL2 +2H2O
& 87 76

m=2.175 g

w=2.175/4.35 * 100 = 50%