& Broup 2
A2 Chemistry Topical Paper 4
Topic 1: Energetics & Group 2
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(ii) The ionic equation for this reaction is shown.
Ca(s) + 2H'(aq)
→ Ca''(aq) + H, (g)
AH = x kJ mot
deur
Construct a fully labelled Hess' Law cycle to connect each side of this equation to the
relevant gas phase ions.
Use your cycle, the following data and data from the Data Booklet. to calculate a value for x.
standard enthalpy of atomisation of Ca(s), AH;(Ca)
+178 kJ mot
standard enthalpy of hydration of Ca-(g), A (Ca) -1576 kJmol
-1090 kJ mot
standard enthalpy of hydration of Hº(9), AH (H)
are with the
all others