Which of the following ions decolorizes acidic $KMnO_4$ solution?

The oxidation state of copper changes when aqueous copper $(II)$ ions react with
$(I)$ $NaOH_{(aq)}$
$(II)$ $Fe_{(s)}$
$(III)$ $KI_{(aq)}$

When $SO_2$ gas is passed through an acidified solution of $K_2Cr_2O_7$,the solution turns........

The pair of compounds that can exist together is

$2KMnO_4 + 3H_2SO_4 + 5H_2O_2 \rightarrow K_2SO_4 + 2MnSO_4 + 8H_2O + 5O_2$. Find the normality of $H_2O_2$ solution,if $20 \ mL$ of it is required to react completely with $16 \ mL$ of $0.02 \ M \ KMnO_4$ solution. (Molar mass of $KMnO_4 = 158 \ g \ mol^{-1}$)

In the following reactions $(i)$ $MnO_2 + 4 HCl \rightarrow$ and $(ii)$ $2 KMnO_4 + 16 HCl \rightarrow$,the number of moles of chlorine gas released respectively are