(a) The energy cycle shown can be used, along with suitable data, to calculate the enthalpy change of hydration of Ca²⁺(g). Each arrow indicates a transformation, W, X, Y and Z. Each transformation consists of one or more steps. [Figure 3.1] The following data and data from the Data Booklet should be used. electron affinity of Cl(g) = -349 kJ mol-1 enthalpy change of atomisation of Ca(s) = +193 kJ mol-1 enthalpy change of formation of CaCl₂(s) = −795kJ mol-1 enthalpy change of solution of CaCl2(s) = -83 kJ mol-1 enthalpy change of hydration of Cl-(g) = -364 kJ mol-1

1. (a)(i)Calculate the value of the enthalpy change corresponding to transformation W. Show your working. enthalpy change W =[2]
2. (a)(ii)Use your answer to (a)(i) and other data to calculate the value of the enthalpy change corresponding to transformation Z. enthalpy change Z =[2]
3. (a)(iii)Use your answer to (a)(ii) to calculate the enthalpy change of hydration of Ca²⁺(g). enthalpy change of hydration of Ca²⁺(g) =[2]
4. (a)(iv)Write an expression, in terms of W, X, Y and/or Z, to show how the enthalpy changes of two of the transformations can be used to calculate the lattice energy of CaCl₂(s). lattice energy of CaCl₂(s) =[1]
5. (a)(v)State whether the lattice energy of CaCl₂(s) is more or less exothermic than the lattice energy of MgF2(s). Explain your answer.[1]
6. (b)The sulfates of the Group 2 elements vary in solubility down Group 2.
7. (b)(i)Give the names of two solutions that could be mixed to form barium sulfate.[1]
8. (b)(ii)State and explain how the solubilities of the sulfates of the Group 2 elements vary down Group 2.[4]

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.