CAIE A Level Chemistry 9701 · Chemical energetics

Chemical energetics: suggest question

Suggest4 marksStandard

The table shows the enthalpy change of hydration of the Group 2 ions $\ce{Mg^{2+}}$ , $\ce{Ca^{2+}}$ , $\ce{Sr^{2+}}$ and $\ce{Ba^{2+}}$ .

Ion	$\Delta H_\text{hyd}$ / kJ mol $^{-1}$
$\ce{Mg^{2+}}$	$-1920$
$\ce{Ca^{2+}}$	$-1650$
$\ce{Sr^{2+}}$	$-1480$
$\ce{Ba^{2+}}$	$-1360$

Suggest why the enthalpy change of hydration becomes less exothermic as the ionic radius increases down the group.

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4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.

Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.

Chemical energetics: suggest question

How this question is marked

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