Adam's catalyst is

What is the role of $MnO_2$ in the decomposition reaction $2KClO_3 \to 2KCl + 3O_2$?

Give four examples of heterogeneous catalysis.

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. $4NH_{3(g)} + 5O_{2(g)} \rightarrow 4NO_{(g)} + 6H_2O_{(g)}$	$I$. $NO_{(g)}$
$B$. $N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)}$	$II$. $H_2SO_{4(l)}$
$C$. $C_{12}H_{22}O_{11(aq)} + H_2O_{(l)} \rightarrow C_6H_{12}O_6 + C_6H_{12}O_6$	$III$. $Pt_{(s)}$
$D$. $2SO_{2(g)} + O_{2(g)} \rightarrow 2SO_{3(g)}$	$IV$. $Fe_{(s)}$

Choose the correct answer from the options given below.

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:

In the oxidation of oxalic acid by $KMnO_4$,the color of $KMnO_4$ disappears slowly at the beginning of the reaction,but then it disappears very rapidly. This is an example of .......