Which catalyst is used in the reaction $2KClO_3 \to 2KCl + 3O_2$?

In aqueous solution,$Na_2SO_3$ is oxidized by air,but $Na_3AsO_3$ is not. However,when air is passed through a solution containing both $Na_2SO_3$ and $Na_3AsO_3$,both are oxidized. This is an example of:

Identify the incorrect pair from the following:

Write the characteristics of a catalyst.

How is Raney nickel,which is used as a catalyst,prepared?

When acidified $KMnO_4$ is added to hot oxalic acid solution,the decolourization is slow in the beginning,but becomes very rapid after some time. This is because :