JEE MAIN - Chemistry (2022 - 26th July Morning Shift - No. 18)
$$2.4 \mathrm{~g}$$ coal is burnt in a bomb calorimeter in excess of oxygen at $$298 \mathrm{~K}$$ and $$1 \mathrm{~atm}$$ pressure. The temperature of the calorimeter rises from $$298 \mathrm{~K}$$ to $$300 \mathrm{~K}$$. The enthalpy change during the combustion of coal is $$-x \mathrm{~kJ} \mathrm{~mol}^{-1}$$. The value of $$x$$ is ___________. (Nearest Integer)
(Given : Heat capacity of bomb calorimeter $$20.0 \mathrm{~kJ} \mathrm{~K}^{-1}$$. Assume coal to be pure carbon)
Answer
200
Explanation
$$\mathrm{Q}($$ Heat evolved $$)=-\frac{\mathrm{C}_{\text {system }} \Delta \mathrm{T}}{\mathrm{n}}$$
$$\mathrm{n}_{\text {coal }}=\frac{2.4}{12}$$
$$\mathrm{Q}=\frac{-20(300-298)}{0.2}$$
$$Q=-200 \mathrm{~kJ} / \mathrm{mol}$$
$$x=200$$
$$\mathrm{n}_{\text {coal }}=\frac{2.4}{12}$$
$$\mathrm{Q}=\frac{-20(300-298)}{0.2}$$
$$Q=-200 \mathrm{~kJ} / \mathrm{mol}$$
$$x=200$$
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