Question

Why is CuSO₄ the expected formula of Copper Sulphate and not Cu₂SO₄ when Copper has variable valency of Cu⁺ and Cu²⁺ ; Here the higher valency is used for the salt.

However in the case of Iron Sulphate the expected formula is FeSO₄ and not Fe₂(SO₄)₃ eventhough Iron also has variable valency of Fe²⁺ and Fe³⁺ ; Here the lesser valency is used for the salt.

Answer 1

Copper generally exists in two oxidation states that is +1 and +2 . Out of these two states +2 state is more stable, infact +1 state spontaneously disproportionates into Cu and Cu+2. Since +1 state of copper is relatively less stable hence we generally see CuSO4 where copper is in +2 state and not Cu2SO4 where copper is found in +1 state