How many moles of $K_2Cr_2O_7$ will be reduced by $1$ mole of $Sn^{2+}$ ions?

In the redox reaction
$x \ MnO + y \ PbO_2 + z \ HNO_3 \to a \ HMnO_4 + b \ Pb(NO_3)_2 + c \ H_2O$
Find the values of $x, y, z$.

In the neutral or faintly alkaline medium,$KMnO_4$ oxidises iodide into iodate. The change in oxidation state of manganese in this reaction is from?

After balancing the equation,$C_2O_4^{2-} + H^+ + MnO_4^- \longrightarrow CO_2 + Mn^{2+} + H_2O$,the coefficient of $CO_2$ is:

For the redox reaction $MnO_4^- + C_2O_4^{2-} + H^+ \longrightarrow Mn^{2+} + CO_2 + H_2O$,the correct coefficients of the reactants for the balanced equation are $MnO_4^-$ - $C_2O_4^{2-}$ - $H^+$

Chlorine undergoes disproportionation in alkaline medium as shown below:
$a Cl_{2(g)} + b OH^{-}_{(aq)} \rightarrow c ClO^{-}_{(aq)} + d Cl^{-}_{(aq)} + e H_2O_{(l)}$
The values of $a, b, c$ and $d$ in a balanced redox reaction are respectively: