The volume, in $\mathrm{mL}$, of $0.02{\mathrm{MK}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$, solution required to react with $0.288\mathrm{g}$ of ferrous oxalate in acidic medium is$\dots \dots \dots \dots$ (Molar mass of $\mathrm{Fe}=56{\mathrm{gmol}}^{-1}$ )
 

A $100 \mathrm{mL}$ solution was made by adding $1.43 \mathrm{g}$ of ${\mathrm{Na}}_2{\mathrm{CO}}_3.{\mathrm{xH}}_2\mathrm{O}.$ The normality of the solution is $0.1 \mathrm{N}$. The value of $\mathrm{x}$ is _______

(The atomic mass of $\mathrm{Na}$ is $23\mathrm{g}/\mathrm{mol}$)

A $20.0 \mathrm{mL}$ solution containing $0.2 \mathrm{g}$ impure ${\mathrm{H}}_2{\mathrm{O}}_2$ reacts completely with $0.316 \mathrm{g}$ of ${\mathrm{KMnO}}_4$ in acid solution. The purity of ${\mathrm{H}}_2{\mathrm{O}}_2$ (in $\mathrm{\%}$) is______  (mol. wt. of ${\mathrm{H}}_2{\mathrm{O}}_2=34$; mol. wt. of ${\mathrm{KMnO}}_4=158$)

In which one of the following sets all species show disproportionation reaction?