Question

Enthalpy of combustion of $CH_4, C_2H_6$ and $C_3H_8$ are $-210, -370$ and $-530\, kcal/mol$ respectively. The approximate value of enthalpy of combustion of $n$-hexane is

• A. $-1170\, \frac{kcal}{mol}$
• B. $-750\, \frac{kcal}{mol}$
• C. $-1010\, \frac{kcal}{mol}$
• D. $-590\, \frac{kcal}{mol}$

Answer 1

Answer: (C)

For each $- CH_2$ the enthalpy of combustion is increased by $160 \,kcal/mol.$
$\therefore \Delta_{comb}H\left(C_{6}H_{6}\right)=-210-5\times160=-1010$ kcal/mol