Problems and exercisesCombustion

1. Balance the combustions

Balance the complete combustion reaction of:

1. Propane, C₃H₈
2. Octane, C₈H₁₈
3. Cyclohexane, C₆H₁₂

2. Which isomer is more stable?

The heats of combustion of butane and 2-methylpropane are −687.4 and −685.4 kcal/mol. Which of the two is more stable? By how much?

3. Heat of formation

Calculate the heat of formation of butane from its heat of combustion (−687.4 kcal/mol, with liquid water) and these data: C(graphite) + O₂ → CO₂, −94.1; H₂ + ½ O₂ → H₂O(g), −57.8; H₂O(g) → H₂O(l), −10.52 kcal/mol.

4. Energy per carbon

If the combustion of an alkane releases on average about 165 kcal/mol per carbon, estimate the heat released by one mole of octane.