The most common zinc mineral contains zinc(II) sulfide, ZnS.

1. (a)(i)Complete the electrons in boxes diagram in Fig. 1.1 to show the electronic configuration of a zinc(II) ion. [Figure 1.1][1]
2. (a)(ii)Complete Fig. 1.2 to show the Born–Haber diagram for the ionic solid ZnS. Include state symbols of relevant species. [Figure 1.2][3]
3. (a)(iii)Describe the trend in the first electron affinity of the Group 16 elements S to Te. Explain your answer.[2]
4. (a)(iv)Explain why the lattice energy, ΔHlatt, of ZnO is more exothermic than that of ZnS.[2]
5. (b)(i)Predict the sign of the entropy change, ΔS®, of the reaction in step 1. Explain your answer.[1]
6. (b)(ii)Use the data in Table 1.1 to calculate ΔS® of the reaction shown in step 2. Table 1.1 chemical ZnO(s) C(s) Zn(l) CO(g) S® / J K⁻¹ mol⁻¹ 43.7 5.7 50.8 197.7 ΔS® = .............................................. J K⁻¹ mol⁻¹[1]
7. (b)(iii)An equation for the direct reduction of ZnS by carbon is shown. 2ZnS(s) + C(s) → 2Zn(l) + CS2(g) ΔH° = +733 kJ mol⁻¹ ΔS° = +218 J K⁻¹ mol⁻¹ This reaction is not feasible at 800°C. Calculate ΔG for this reaction at 800°C. ΔG = .............................................. kJ mol⁻¹[2]
8. (c)(i)Construct an equation for the thermal decomposition of Zn(NO3)2.[1]
9. (c)(ii)The radii of some Group 2 cations and Zn²⁺ are shown in Table 1.2. Table 1.2 cation Mg²⁺ Ca²⁺ Sr²⁺ Ba²⁺ Zn²⁺ radius/pm 65 99 113 135 74 State and explain the trend in thermal stability of the Group 2 nitrates down the group.[2]
10. (c)(iii)Use Table 1.2 to suggest which Group 2 nitrates are less thermally stable than zinc nitrate.[1]

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