$H_2O_2$ reduces $MnO_4^-$ ion to:

Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

$2 MnO_4^{-} + bI^{-} + cH_2O \rightarrow xI_2 + yMnO_2 + zOH^{-}$
If the above equation is balanced with integer coefficients,the value of $z$ is . . . . . .

Fluorine reacts with ice and results in the change:
$H_2O_{(s)} + F_{2(g)} \rightarrow HF_{(g)} + HOF_{(g)}$
Justify that this reaction is a redox reaction.

Observe the following reaction:
$xS_{8\text{(s)}} + yOH^{-}{_{\text{(aq)}}} \rightarrow zS^{2-}{_{\text{(aq)}}} + 2S_2O_3^{2-}{_{\text{(aq)}}} + 6H_2O_{\text{(l)}}$
Find the values of $x, y$ and $z$ respectively.

Write the redox reaction that occurs when a zinc rod is placed in a $H_2SO_4$ solution.