In the balanced chemical reaction
$IO_3^- + aI^- + bH^+ \to cH_2O + dI_2$
$a, b, c, d$ respectively correspond to

What is the equivalent weight of hydrochloric acid in the given redox reaction $MnO_2 + 4HCl \to MnCl_2 + 2H_2O + Cl_2$?
If the molar mass of hydrochloric acid is $M$.

In the ionic equation $BiO_{3}^{-} + 6H^{+} + x e^{-} \longrightarrow Bi^{3+} + 3H_{2}O$,the value of $x$ is:

For the reaction:
$I^{-} + ClO_{3}^{-} + H_{2}SO_{4} \longrightarrow Cl^{-} + HSO_{4}^{-} + I_{2}$
The correct statement$(s)$ in the balanced equation is/are:
$A$. Stoichiometric coefficient of $HSO_{4}^{-}$ is $6$.
$B$. Iodide is oxidized.
$C$. Sulphur is reduced.
$D$. $H_{2}O$ is one of the products.

How many electrons are lost in the following transformation?
$3Fe + 4H_2O \to Fe_3O_4 + 4H_2$

In the reaction $2CuSO_4 + 4KI \rightarrow Cu_2I_2 + 2K_2SO_4 + I_2$,what is the ratio of the equivalent weight of $CuSO_4$ to its molecular weight?