This should have been a reasonably straight forward calculation, but care needs to be taken to get the right structures and the right molecular formula, then do the math correctly.

a. C5H10 + 15/2 O2 --> 5 CO2 + 5 H2O
(2 marks)

b. The calculation is shown on the figure below. (3 marks)

c. The values are matched on the figure below. (2 marks)

d.(3 marks)

Hess`s law figure

e. Stability will be affected by the degree of branching (more stronger primary C-H bonds will cause a more stable molecule) and the steric interactions between the groups (from the molecular models experiment). Based on branching, isomers i and ii are more stable than isomer iii since they have one more branch. The difference between i and ii is due to the cis and trans nature of the methyl groups. In isomer i where the methyl groups are cis, the two methyl groups are held in the unfavourable eclipsed position which destablises isomer i with respect to isomer ii. (2 marks)

f. (1 mark)

Common errors:

In part a:

In part d :