Question

What happens when
(i) Manganate ions ( MnO₄²⁻ ) undergoes disproportionation reaction in acidic medium?
(ii) Lanthanum is heated with Sulphur?

Answer 1

Reactions

Explanation:

(i) The important factor which decides whether a substance will undergo disproportionation reaction or not is its ability to undergo multiple oxidation state. As Mn can undergo multiple oxidation state, it can undergo disproportionation reaction.

MnO2-4 ions disproportionate in acidic medium to give Permanganate ions and Manganese (IV) oxide.

3MnO42- + 4H+ → 2mnO-4 +MnO2 + 2H2O

(ii)  When Lanthanum is heated with Sulphur, Lanthanum sulphide if formed.

2La + 3S + heat → La2S3

Answer 2

Answer:

Since, +2 oxidation state is more stable as compared to +3 oxidation state due to stable half filled electronic configuration, therefore Mn(III) disproportionates to Mn(II).