$(Molarity$ $\times$ $volume$ $\times$ $n.f)$ of $K _{2} Cr _{2} O _{7}=$ (molarity $\times$ volume $\times$ n.f ) of $Fe ^{2+}$
$0.02 \times 20 \times 6= M \times 10 \times 1$
$M =0.24$
Molarity $=24 \times 10^{-2}$
$\mathrm{Cr}_2 \mathrm{O}_7^{2-}+\mathrm{XH}^{+}+\mathrm{Ye}^{-} \rightarrow 2 \mathrm{~A}+\mathrm{ZH}_2 \mathrm{O}$
$\mathrm{X}, \mathrm{Y}, \mathrm{Z}$ અને $\mathrm{A}$ અનુક્કમે (ક્રમશઃ) શોધો.
$14{H^ + } + C{r_2}O_7^{2 - } + 3Ni \to 2C{r^{3 + }} + 7{H_2}O + 3N{i^{2 + }}$
$S{O_2}\, + \,\,2{H_2}S\,\,\, \to \,\,3S\,\, + \,\,2{H_2}O$