(a)[1]
Calculate the relative formula mass, $M_r$, for Cu$_2$FeSnS$_4$.
(b)[1]
Calculate the percentage by mass of tin in SnO$_2$.
(c)[1]
Use this information together with your answer to (b) to suggest whether it would be better to extract tin from SnO$_2$ or Cu$_2$FeSnS$_4$. Explain your answer.
(d)[2]
Write the chemical equation for this reaction.
(e)[2]
Complete the ionic equations. If no reaction occurs, write 'no reaction'. Fe + Sn$^{2+}$ → Sn + Cu$^{2+}$ →
(f)[5]
Describe a test for oxygen. Name the other gaseous product. Describe its appearance. Write the chemical equation for the thermal decomposition of copper(II) nitrate.
(g)[4]
Explain why the iron does not rust when it is fully coated with zinc. Explain why the iron still does not rust after the zinc is scratched.