Page 379 - SUBSEC October 2017_Neat
P. 379
- 6 -
(c) The following diagram represents the Born Haber cycle for the formation of compound
MX(s). DO NOT WRITE IN THIS AREA
–1
The associated enthalpy changes in kJ mol for the cycle above are as follows:
∆H M(s) = + 86; ∆H M(g) = + 408; ∆H (MX(s)) = – 431; ∆H X = + 122; ∆H X(g) = –372
2
(i) State Hess’ Law of heat summation.
................................................................................................................................. DO NOT WRITE IN THIS AREA
.................................................................................................................................
[1 mark]
(ii) Define standard enthalpy change of formation.
................................................................................................................................
................................................................................................................................
[1 mark]
(iii) Which enthalpy values correspond to EACH of the stages I, III and IV in the cycle
above?
.................................................................................................................................
.................................................................................................................................
[3 marks] DO NOT WRITE IN THIS AREA
(iv) Define lattice energy.
.................................................................................................................................
.................................................................................................................................
[1 mark]
GO ON TO THE NEXT PAGE
02112020/CAPE/SPEC 2017
‘‘*’’Barcode Area”*”
Sequential Bar Code
