JEE MAIN - Chemistry (2022 - 26th June Morning Shift - No. 12)
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
727
Explanation
$\mathrm{CH}_{3} \mathrm{OH}(\mathrm{l})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
$$ \begin{aligned} &\Delta \mathrm{H}=\Delta \mathrm{U}+\Delta \mathrm{n}_{\mathrm{g}} \mathrm{RT} \\\\ &=-726 \mathrm{~kJ}+\left(\frac{-1}{2}\right) \times 8.3 \times 300 \\\\ &\simeq-727 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned} $$
$$ \begin{aligned} &\Delta \mathrm{H}=\Delta \mathrm{U}+\Delta \mathrm{n}_{\mathrm{g}} \mathrm{RT} \\\\ &=-726 \mathrm{~kJ}+\left(\frac{-1}{2}\right) \times 8.3 \times 300 \\\\ &\simeq-727 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned} $$
Comments (0)
