Calculate the mass of impure copper used for the experiment.
Name the vessel in which solution $J$ should be prepared.
Consult the diagrams to fill in the results table and work out the mean volume of $0.100\,\text{mol dm}^{-3}$ $\text{Na}_2\text{S}_2\text{O}_3$.
Calculate how many moles of $\text{Na}_2\text{S}_2\text{O}_3$ are present in the average volume.
Use equation $3$ to find the number of moles of $I_2$ in $25.0\,\text{cm}^3$ of $J$.
Calculate how many moles of $I_2$ are in $250\,\text{cm}^3$ of $J$.
Use equation $2$ to work out the number of moles of $\text{Cu(NO}_3)_2$ that generate this amount of $I_2$.
Use equation $1$ to deduce the number of moles of $\text{Cu}$.
Calculate the mass of copper present in the impure-copper sample. [$A_r: \text{Cu},\,63.5$]
Calculate the percentage by mass of copper in the impure-copper sample.