Number of moles of $MnO_4^-$ required to oxidize one mole of ferrous oxalate completely in acidic medium will be .......... $moles$.

What is '$A$' in the following reaction?
$2Fe^{3+} + Sn^{2+} \to 2Fe^{2+} + A$

Observe the following reaction:
$aP_4{_{\text{(s)}}} + bOH^{-}{_{\text{(aq)}}} + cH_2O_{\text{(l)}} \rightarrow dPH_3{_{\text{(g)}}} + eH_2PO_2^{-}{_{\text{(aq)}}}$
The values of $a, b, c,$ and $d$ are respectively:

In the titration of $KMnO_{4}$ and oxalic acid in acidic medium,the change in oxidation number of carbon at the end point is

In mildly alkaline medium,thiosulphate ion is oxidized by $MnO_4^-$ to $A$. The oxidation state of sulphur in $A$ is ..... .

Assign $A$,$B$,$C$,$D$ from given type of reaction.
$Zn_{(s)} + 2HCl_{(aq)} \longrightarrow ZnCl_{2(aq)} + H_{2(g)}$