For complete combustion of methanol
CH3OH(I) + ${3 \over 2}$O2(g) $\to$ CO2(g) + 2H2O(I)
the amount of heat produced as measured by bomb calorimeter is 726 kJ mol$-$1 at 27$^\circ$C. The enthalpy of combustion for the reaction is $-$x kJ mol$-$1, where x is ___________. (Nearest integer)
(Given : R = 8.3 JK$-$1 mol$-$1)
Answer (integer)
727
Solution
$\mathrm{CH}_{3} \mathrm{OH}(\mathrm{l})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
<br/><br/>
$$
\begin{aligned}
&\Delta \mathrm{H}=\Delta \mathrm{U}+\Delta \mathrm{n}_{\mathrm{g}} \mathrm{RT} \\\\
&=-726 \mathrm{~kJ}+\left(\frac{-1}{2}\right) \times 8.3 \times 300 \\\\
&\simeq-727 \mathrm{~kJ} \mathrm{~mol}^{-1}
\end{aligned}
$$
About this question
Subject: Chemistry · Chapter: Thermodynamics · Topic: Zeroth and First Law
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