Consider the titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as an indicator. The number of moles of Mohr's salt required per mole of dichromate is

To measure the quantity of ${\mathrm{MnCl}}_2$ dissolved in an aqueous solution, it was completely converted into ${\mathrm{KMnO}}_4$ using the reaction ${\mathrm{MnCl}}_2+{\mathrm{K}}_2{\mathrm{S}}_2{\mathrm{O}}_8+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{KMnO}}_4+{\mathrm{H}}_2{\mathrm{SO}}_4+\mathrm{HCl}$ (the equation is not balanced). Few drops of concentrated $\mathrm{HCl}$ were added to this solution and gently warmed. Further, the oxalic acid ($225 \mathrm{mg}$) was added in portions till the colour of the permanganate ion disappeared. The quantity of ${\mathrm{MnCl}}_2$ (in $\mathrm{mg}$) present in the initial solution is ____. 

(Atomic weights in $\mathrm{g} {\mathrm{mol}}^{–1}\text{:} \mathrm{Mn}=55, \mathrm{Cl}=35.5$)

Consider the following reaction: 

$x{\mathrm{MnO}}_4^{-}+y{C}_2{\mathrm{O}}_4^{2-}+z{H}^{+}\to x{\mathrm{Mn}}^{2+}+2y{\mathrm{CO}}_2+\frac{z}{2}{\mathrm{H}}_2\mathrm{O}$ 

The values of $x$, $y$ and z in the reaction are, respectively: 

$25 \mathrm{mL}$ of the given $\mathrm{HCl}$ solution requires $30 \mathrm{mL}$ of $0.1 \mathrm{M}$ sodium carbonate solution. What is the volume of this $\mathrm{HCl}$ solution required to titrate $30 \mathrm{mL}$ of $0.2 \mathrm{M}$ an aqueous $\mathrm{NaOH}$ solution?