$18$: :An impure sample of iron$($ II $)$ sulphate was analysed by titration.

The sample was dissolved in $25\mathrm{.}0cm3$ of dilute sulphuric acid and then titrated against $0\mathrm{.}0400mo\frac{l}{d}m3$ potassium dichromate$($ VI$)$ solution. $19\mathrm{.}0cm3$ of potassium dichromate$($ VI$)$ solution was required to reach the end$-$point.

$($i$)$ Calculate the number of moles of potassium dichromate$($VI$)$ used in the titration.

$($ii$)$One mole of potassium dichromate$($ VI$)$ reacts with six moles of iron$($II$)$ ions.

Calculate the mass, in grams, of iron$($ II $)$ ions in the sample analysed.