**Part
8: THERMODYNAMICS**

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. **C_{6}H_{12} + 9 O_{2} --> 6 CO_{2} + 6 H_{2}O

**b. **The calculation is shown on the figure below.

**c**.

**d**. See diagram above.

**e**. The difference between the 3 isomers is in the degree of branching. Hex-1-ene** i **is the least branched and the least stable (DH_{f} = -10.0 kcal/mol) in contrast to isomer **iii** 3,3-dimethylbut-1-ene (DH_{f} = -14.3 kcal/mol) which is more branched. A more branched isomer has more primary C-H bonds which are stronger than secondary C-H which in turn are stronger than tertiary C-H.

**f. **

**Common errors**:

In part** a**:

- did not show the right products from the combustion reaction (
*i.e.*CO_{2}and H_{2}O) - did not balance the coefficients
- wrong molecular formula for hex-1-ene

In part** d** :

- Incorrect math,
*e.g.*using 18 H_{2}instead of 9. - getting the signs wrong