Aqueous solutions of hydrogen sulphide and sulphur dioxide when mixed together,yield

Assign $A, B, C, D$ from the given type of reaction.
$Na_2CO_3 + PbSO_4 \longrightarrow PbCO_3 \downarrow + Na_2SO_4$

If the molecular weights of $Na_2S_2O_3$ and $I_2$ are $M_1$ and $M_2$ respectively, then what will be the equivalent weights of $Na_2S_2O_3$ and $I_2$ in the following reaction?
$2S_2O_3^{2-} + I_2 \longrightarrow S_4O_6^{2-} + 2I^-$

What is the equivalent weight of $SnCl_{2}$ in the following reaction: $SnCl_{2} + Cl_{2} \longrightarrow SnCl_{4}$?

What is the value of $x$ in order to balance the following redox reaction?
$Mn_{(aq)}^{2+} + x ClO_{3_{(aq)}}^{-} \rightarrow MnO_{2_{(s)}} + x ClO_{2_{(aq)}}$

What will be the coefficients $x, y, z$ in the balanced form of the following redox equation: $xIO_3^- + yHSO_3^- \to zI^{-} + pH^{+} + qSO_4^{2-}$?