Identify the statement which is not correct regarding copper sulphate.

The yellow colour solution of $Na_2CrO_4$ changes to orange-red on passing $CO_2$ gas due to the formation of $:-$

Given below are two statements:
Statement $I$: Fusion of $MnO_2$ with $KOH$ and an oxidising agent gives dark green $K_2MnO_4$.
Statement $II$: Manganate ion on electrolytic oxidation in alkaline medium gives permanganate ion.
In the light of the above statements,choose the correct answer from the options given below.

Which of the following are used as catalysts in petroleum cracking?

For $Cu_{2}Cl_{2}$ and $CuCl_{2}$ in aqueous medium,which of the following statements is correct?

Identify the incorrect statement.