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]