From the following data, calculate the enthalpy change (in kJ/mol) for the combustion of cyclopropan — Thermodynamics and Thermochemistry Chemistry Question
Question
From the following data, calculate the enthalpy change (in kJ/mol) for the combustion of cyclopropane(g) at 298 K. The enthalpy of formation of $\text{CO}_2\text{(g)}$, $\text{H}_2\text{O(l)}$ and propene(g) are –394, –286 and 20 kJ/mol, respectively. The enthalpy of isomerization of cyclopropane(g) to propene(g) is –33 kJ/mol.
Answer: B
💡 Solution & Explanation
Enthalpy of isomerization $\text{cyclopropane} \to \text{propene}$ is -33 kJ/mol. $\Delta H_f(\text{propene}) - \Delta H_f(\text{cyclopropane}) = -33 \implies 20 - \Delta H_f(\text{cyclopropane}) = -33 \implies \Delta H_f(\text{cyclopropane}) = 53\text{ kJ/mol}$. Combustion of cyclopropane ($\text{C}_3\text{H}_6$): $\Delta H_c = 3(-394) + 3(-286) - 53 = -1182 - 858 - 53 = -2093\text{ kJ/mol}$.
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