Oxidation of manganese(II) sulfate

Chemicals needed

manganese(II) sulfate Xn R 48/20/22 S (2)-22

sodium hydroxide solution 7.5% C R 35 S (1/2)-26-37/39-45

hydrogen peroxide solution 3.5%

Equipment needed

test tube

Test procedure

Safety goggles!
One puts a small spatula-tipful manganese(II) sulfate in a test tube and then adds approx. 1 ml diluted sodium hydroxide solution. A brown manganese(II) hydroxide is very easily formed.
Now one adds about 1 ml of hydrogen peroxide solution, accompanied by a strong gas evolution the solution becomes deep brown and turbid. If wished, one can with a glowing splint test verify that the gas created is oxygen.

Disposal

The diluted reaction mixture can be discharged into the drainage.

Elucidation

Hydrogen peroxide in an alkaline milieu acts oxidizing towards manganese(II), the result is manganese(IV) oxide. That oxygen escapes is to be attributed to the fact that manganese(IV) oxide catalyzes the decomposition of hydrogen peroxide.

Mn(OH)2 + H2O2 --> MnO2.H2O + H2O

2 H2O2 --> 2 H2O + O2

Photos

Precipitation of manganese(IV) oxide and development of oxygen

Literature

derived from experiment 5., "MnSO4 + H2O2",p.83, [7]