Potassium permanganate is a strong oxidising agent, its oxidising action differs in different reaction medium.
In neutral medium:
In neutral medium, it is reduced to MnO₂
MnO₄^- + 2H₂O + 3e^- ⟶ MnO₂ + 4OH^-
(i) It oxidises H₂S to sulphur
2MnO₄^- + 3H₂S ⟶ 2MnO₂ + 3S + 2OH^- + 2H₂O
(ii) It oxidises thiosulphate into sulphate
8MnO₄^- + 3S₂O₃^-2 + H₂O ⟶ 6SO₄^-2 + 8MnO₂ + 2OH^-

In this method aqueous solution of potassium manganate is electrolyzed in the presence of little alkali.
K₂MnO₄ ⇌ 2K⁺ + MO₄^2-
H₂O ⇌ H⁺ + OH^-
Manganate ions are converted into permanganate ions at anode.

H₂ is liberated at the cathode.
2H⁺ + 2e^- ⟶ H₂ ↑
The purple coloured solution is concentrated by evaporation and forms crystals of potassium permanganate on cooling.

Potassium permanganate is prepared from pyrolusite (MnO₂) ore. The preparation involves the following steps
(i) Conversion of MnO₂ to potassium manganate: Powdered ore is fused with KOH in the presence of air or oxidising agents like KNO₃ or KCIO₃. A green coloured potassium manganate is formed.

(ii) Oxidation of potassium manganate to potassium permanganate: Potassium manganate thus obtained can be oxidised in two ways, either by chemical oxidation or electrolytic oxidation.

(i) When potassium dichromate is heated with any chloride salt in the presence of Conc. H₂SO₄, orange red vapours of chromyl chloride (CrO₂CI₂) is evolved.
(ii) This reaction is used to confirm the presence of chloride ion in inorganic qualitative analysis

(iii) The chromyl chloride vapours are dissolved in sodium hydroxide solution and then acidified with acetic acid and treated with lead acetate. A yellow precipitate of lead chromate is obtained

(i) They are hard and show electrical land thermal conductivity.
(ii) They have high melting points higher than those of pure metals.
(iii) Transition metal hydrides are used as powerful reducing agents.
(iv) Metallic carbides are chemically inert