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

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

In the chemical reaction between stoichiometric quantities of $KMnO_4$ and $KI$ in a weakly basic or neutral solution,what is the number of moles of $I_2$ released for $4$ moles of $KMnO_4$ consumed?

The number of electrons required to balance the following equation $NO_3^- + 4H^+ + x e^- \to 2H_2O + NO$ is

The number of moles of acidified $KMnO_4$ required to convert one mole of sulphite ion into sulphate ion is

When $SO_{2}$ is passed through acidified $K_{2}Cr_{2}O_{7}$,the process that takes place is