Question

The heat of combustion of ethane and benzene is -1560 and -3268 kJ $mol-1$ respectively. Which of two has higher efficiency as fuel per gram and the amount of heat produced per gram?

• A. Beneze, $41.9kJ{g}^{-1}$
• B. Ethane, $52kJ{g}^{-1}$
• C. Beneze, $78kJ{g}^{-1}$
• D. Ethane, $30kJ{g}^{-1}$

Answer 1

The correct option is B Ethane, $52kJ{g}^{-1}$

Heat of combustion of ethane $\left(C_2{H}_6\right)=-1560Kjmo{l}^{-1}$

efficiency per gram $=\frac{-1560}{molarmass}$

$=\frac{1560}{30}=52KJ/g$

heat of combustion of benzene $\left(C_6{H}_6\right)=-3268Kjmo{l}^{-1}$

Efficiency $=\frac{3268}{78}=41.9KJ/g$

Ethane has higher efficiency $52KJ/g$