Which of the following reagents causes the aqueous colored solution of acidic $KMnO_4$ to become colorless?

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.

The oxidation state of chromium in the final product formed in the reaction between $KI$ and acidified $K_{2}Cr_{2}O_{7}$ solution is:

Explain the balancing of a redox reaction by the oxidation number method.

Molecular weight of $Cu_2S$ is $M$. In the following reaction its equivalent weight is $M / x$. What is $x$?
$Cu_2S + MnO_4^{-} \rightarrow Cu^{2+} + Mn^{2+} + SO_2$

$MnO_4^{-}$ reacts with $A^{x+}$ to form $AO_3^{-}$,$Mn^{2+}$ and $O_2$. One mole of $MnO_4^{-}$ oxidizes $1.25$ moles of $A^{x+}$ to $AO_3^{-}$. What is the value of $x$?