Question

With increase in number of carbon atoms in alkanes, heat of combustion:

• A. increases
• B. decreases
• C. does not change
• D. changes cant be predicted

Answer 1

Answer: (A)

increases

With the increase in a number of carbon atoms in alkanes, the heat of combustion increases.

This is because, with increase in the number of carbon atoms, the number of binds broken/formed increases due to which the heat of combustion increases.

Thus, the heat of combustion of methane, ethane and butane are $-80.4kJ/mol,-1580.0kJ/mol$ and $-2875.84kJ/mol$ respectively.

Option A is correct.