This question is about the determination of the formula of a metal oxide. A student heats a known mass of magnesium in a crucible. The student records the mass of the magnesium and the mass of the magnesium oxide formed. [Figure 4 referenced - implicitly, this experiment often uses a crucible and lid, but no diagram is shown in the question paper for Q17 directly, rather the description is given.]

1. (a)(i)State one safety precaution the student should take during this experiment.[1]
2. (a)(ii)Explain why it is necessary to lift the lid of the crucible occasionally during heating.[2]
3. (a)(iii)Explain why the student heats the crucible to constant mass.[2]
4. (b)(i)A student performs the experiment using zinc. The student records these results. Mass of empty crucible = 15.36 g Mass of crucible + zinc = 16.01 g Mass of crucible + zinc oxide = 16.41 g Calculate the mass of zinc used.[1]
5. (b)(ii)Calculate the mass of oxygen that reacted.[1]
6. (b)(iii)Calculate the amount in moles of zinc atoms that reacted. [Aᵣ: Zn = 65, O = 16][1]
7. (b)(iv)Calculate the amount in moles of oxygen atoms that reacted. [Aᵣ: Zn = 65, O = 16][1]
8. (b)(v)Deduce the empirical formula of zinc oxide.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.