Thermodynamics and Thermochemistry 2 Question 27
27. The standard molar heat of formation of ethane, carbon dioxide and liquid water are $-21.1,-94.1$ and $-68.3 \mathrm{kcal}$ respectively. Calculate the standard molar heat of combustion of ethane.
(1986, 2M)
Show Answer
Solution:
- $\Delta H=\Sigma \Delta H_{f}^{\circ}$ (products) $-\Sigma \Delta H_{f}^{\circ}$ (reactants)
$$ \begin{aligned} & =-2 \times 94.1-3 \times 68.3-(-21.1) \ & =-372 \mathrm{kcal} / \mathrm{mol} \end{aligned} $$
