Thermodynamics and Thermochemistry 2 Question 5
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5. For the complete combustion of ethanol, $\mathrm{C}{2} \mathrm{H}{5} \mathrm{OH}(l)+3 \mathrm{O}{2}(g) \longrightarrow 2 \mathrm{CO}{2}(g)+3 \mathrm{H}{2} \mathrm{O}(l)$, the amount of heat produced as measured in bomb calorimeter, is $1364.47 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at $25^{\circ} \mathrm{C}$. Assuming ideality the enthalpy of combustion, $\Delta{C} H$, for the reaction will be $\left(R=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$
======= ####5. For the complete combustion of ethanol, $\mathrm{C}{2} \mathrm{H}{5} \mathrm{OH}(l)+3 \mathrm{O}{2}(g) \longrightarrow 2 \mathrm{CO}{2}(g)+3 \mathrm{H}{2} \mathrm{O}(l)$, the amount of heat produced as measured in bomb calorimeter, is $1364.47 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at $25^{\circ} \mathrm{C}$. Assuming ideality the enthalpy of combustion, $\Delta{C} H$, for the reaction will be $\left(R=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$
3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed (a) $-1366.95 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(b) $-1361.95 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(c) $-1460.50 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(d) $-1350.50 \mathrm{~kJ} \mathrm{~mol}^{-1}$
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Solution:
- $\mathrm{C}{2} \mathrm{H}{5} \mathrm{OH}(l)+3 \mathrm{O}{2}(g) \longrightarrow 2 \mathrm{CO}{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(l)$
$$ \begin{aligned} \Delta U & =-1364.47 \mathrm{~kJ} / \mathrm{mol} \ \Delta H & =\Delta U+\Delta n_{g} R T \ \Delta n_{g} & =-1 \ \Delta H & =-1364.47+\frac{-1 \times 8.314 \times 298}{1000} \end{aligned} $$
[Here, value of $R$ in unit of $\mathrm{J}$ must be converted into $\mathrm{kJ}$ ]
$$ \text { or } \quad=-1366.95 \mathrm{~kJ} / \mathrm{mol} $$
