JEE PYQ: Chemical Equilibrium Question 2
Question 2 - 2021 (17 Mar Shift 1)
The standard enthalpies of formation of $\text{Al}_2\text{O}_3$ and CaO are $-1675 \text{ kJ mol}^{-1}$ and $-635 \text{ kJ mol}^{-1}$ respectively. For the reaction
$3\text{CaO} + 2\text{Al} \rightarrow 3\text{Ca} + \text{Al}_2\text{O}_3$
the standard reaction enthalpy $\Delta_r H^\circ =$ ____ kJ. (Round off to the Nearest Integer).
Show Answer
Answer: 230
Solution
$\Delta H^\circ = [1 \times (-1675) + 3 \times 0] - [3 \times (-635) + 2 \times 0] = -1675 + 1905 = +230 \text{ kJ mol}^{-1}$
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