A thermodynamic system absorbs 20 kJ of heat and simultaneously does 10 kJ of expansion work on its — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

According to the IUPAC sign convention for the First Law of Thermodynamics, $\Delta U = q + w$. Heat absorbed by the system is positive ($q = +20 \text{ kJ}$). Work done by the system on the surroundings is negative ($w = -10 \text{ kJ}$). Therefore, $\Delta U = +20 + (-10) = +10 \text{ kJ}$. The internal energy increases by 10 kJ.