In acidic medium,one mole of $MnO_4^-$ accepts how many moles of electrons in a redox process?

The equivalent weight of ${S_2O_3^{2-}}$ in the reaction where it acts as a reductant is ...... . ${2S_2O_3^{2-} + I_2 \rightarrow S_4O_6^{2-} + 2I^-}$

Assertion: Change in color of acidic solution of potassium dichromate by breath is used to test drunk drivers.
Reason: Change in color is due to the complexation of alcohol with potassium dichromate.

For the balanced chemical reaction: $IO_3^- + aI^- + bH^+ \to cH_2O + dI_2$,what are the values of $a, b, c$ and $d$ respectively?

Treatment of alkaline $KMnO_{4}$ solution with $KI$ solution oxidises iodide to:

$2 MnO_{4}^{-} + b C_{2}O_{4}^{2-} + c H^{+} \rightarrow x Mn^{2+} + y CO_{2} + z H_{2}O$
If the above equation is balanced with integer coefficients,the value of $c$ is ...........
(Round off to the Nearest Integer).