Question

when 1 mol of a fuel burns at constant pressure, it produces 3452 kj of heat and does 11 kj of work. what are the values of δu and δh for the combustion of the fuel?

Explanation:

Step1: Calculate $\Delta H$

At constant pressure, $\Delta H = q_p$. Here, $q_p=- 3452\ \text{kJ}$ (negative because heat is released). So, $\Delta H=-3452\ \text{kJ}$.

Step2: Calculate $\Delta U$

Use the first - law of thermodynamics $\Delta U=q + w$. Given $q = q_p=-3452\ \text{kJ}$ and $w=-11\ \text{kJ}$ (work done by the system). Then $\Delta U=-3452\ \text{kJ}+(- 11\ \text{kJ})$.

Answer:

$\Delta H=-3452\ \text{kJ}$ and $\Delta U=-3463\ \text{kJ}$