Balance the following redox reaction by the ion-electron method:

${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}\left(\mathrm{aq}\right)+{{\mathrm{SO}}_3}^{2-}\left(\mathrm{aq}\right) \to {\mathrm{Cr}}^{3+}\left(\mathrm{aq}\right)+{{\mathrm{SO}}_4}^{2-}\left(\mathrm{aq}\right)$ (in acidic solution)

For the redox reaction

${\mathrm{xMnO}}_4^{-}+{\mathrm{yH}}_2{\mathrm{C}}_2{\mathrm{O}}_4+{\mathrm{zH}}^{+}\to {\mathrm{mMn}}^{2+}+{\mathrm{nCO}}_2+{\mathrm{pH}}_2\mathrm{O}$

The reaction of sulphur in alkaline medium is given below:

${\mathrm{S}}_{8\left(\mathrm{s}\right)}+\mathrm{a} {\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-}\to \mathrm{b} {\mathrm{S}}_{\left(\mathrm{aq}\right)}^{2-}+\mathrm{c} {\mathrm{S}}_2{\mathrm{O}}_{3\left(\mathrm{aq}\right)}^{2-}+\mathrm{d} {\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}$

The values of '$a$' is______ (Integer answer)

What are $\mathrm{x}$ and $\mathrm{y}$ in the following reaction?

$\mathrm{x} {\mathrm{Pb}}_3{\mathrm{O}}_4\to \mathrm{yPbO}+{\mathrm{O}}_2$

What are the coefficients $\mathrm{x}\text{,} \mathrm{y}\text{,} \mathrm{z}\text{,} \mathrm{p}\text{,} \mathrm{q}\text{,} \mathrm{r}$ and $\mathrm{s}$, respectively, in the following balanced equation?

${\mathrm{xHNO}}_{2\left(\mathrm{aq}\right)}+{\mathrm{yKMnO}}_{4\left(\mathrm{aq}\right)}+{\mathrm{zH}}_2{\mathrm{SO}}_{4\left(\mathrm{aq}\right)}\to {\mathrm{pHNO}}_{3\left(\mathrm{aq}\right)}+\mathrm{q} {\mathrm{K}}_2{\mathrm{SO}}_{4\left(\mathrm{aq}\right)}+{\mathrm{rMnSO}}_{4\left(\mathrm{aq}\right)}+{\mathrm{sH}}_2{\mathrm{O}}_{\left(\mathrm{II}\right)}$

The coefficients $x, y$ and $z$ in the given redox reaction are respectively

$x{\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}+y{\mathrm{SO}}_2+z{\mathrm{H}}^{+}\to {\mathrm{Cr}}^{+3}+{\mathrm{SO}}_4^{2-}+{\mathrm{H}}_2\mathrm{O}$

In the balanced equation of the following reaction, the ratio of $\mathrm{a}/\mathrm{b}$ is 

 ${\mathrm{aCaCO}}_3+{\mathrm{bH}}_3{\mathrm{PO}}_4\to {\mathrm{pCa}}_3{\left({\mathrm{PO}}_4\right)}_2+{\mathrm{qCO}}_2+{\mathrm{rH}}_2\mathrm{O}$

Consider the reaction

${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}+{\mathrm{xH}}^{+}+{\mathrm{Fe}}^{2+}\stackrel{}{\to }{\mathrm{yFe}}^{3+}+2{\mathrm{Cr}}^{3+}+{\mathrm{zH}}_2\mathrm{O}$

Sum of $\mathrm{x},\mathrm{y} \mathrm{and} \mathrm{z}$ are