Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is

From the given reaction:
$2 KMnO_4 + 3 H_2 SO_4 + 5 H_2 O_2 \longrightarrow K_2 SO_4 + 2 MnSO_4 + 8 H_2 O + 5 O_2$
Find the normality of $H_2 O_2$ solution,if $20 \ mL$ of it is required to react completely with $16 \ mL$ of $0.02 \ M \ KMnO_4$ solution.
$(Molar \ mass \ of \ KMnO_4 = 158 \ g \ mol^{-1})$

Match the following Column-$I$ $(Half Reaction)$ to Column-$II$ $(n-factor)$.

Column-$I$	Column-$II$
$A$. $C_2O_4^{2-} \rightarrow 2CO_2$	$P$. $2$
$B$. $Cr_2O_7^{2-} + 14H^{+} \rightarrow 2Cr^{3+}$	$Q$. $6$
$C$. $2Na_2S_2O_3 \rightarrow Na_2S_4O_6$	$R$. $3$
$D$. $MnO_4^{-} \rightarrow MnO_2$	$S$. $1$

If an iron rod is dipped in $CuSO_4$ solution,what happens?

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

The set of coefficients of $P_4$,$OH^{\Theta}$ and $H_2PO_2^{\Theta}$ in the balanced reaction $P_4 + OH^{\Theta} \to PH_3 + H_2PO_2^{\Theta}$ is