For the combustion of propane gas, , carried out at a constant temperature, what is the value of ? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The fundamental relationship is $\Delta H = \Delta U + \Delta n_g RT$. We only count gaseous moles for $\Delta n_g$. $\Delta n_g = (\text{moles of gaseous products}) - (\text{moles of gaseous reactants}) = 3 - (1 + 5) = -3$. Therefore, $\Delta H - \Delta U = -3RT$.