The value of of is (in kcal/mol) — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The standard combustion exclusively yields $\text{CO}_2$ and $\text{H}_2\text{O}$: $\text{C}_8\text{H}_{18}\text{(l)} + 12.5\text{O}_2\text{(g)} \to 8\text{CO}_2\text{(g)} + 9\text{H}_2\text{O(g)}$. $\Delta_c H = 8(-94.0) + 9(-58.0) - (-74.0) = -752.0 - 522.0 + 74.0 = -1200.0\text{ kcal/mol}$.