Chemistry - Thermodynamics - I Question with Solution | TestHub

$\Delta {\mathrm{U}}_{\mathrm{AB}}={\mathrm{q}}_{\mathrm{AB}}+{\mathrm{W}}_{\mathrm{AB}}=2+(-5)=-3\mathrm{kJ}/\mathrm{mol}$ $\Delta {\mathrm{U}}_{\mathrm{BC}}=-5\mathrm{kJ}/\mathrm{mol}$ For cyclic process, $\Delta \mathrm{U}=0$ $\begin{array}{rl}& \Delta {\mathrm{U}}_{\mathrm{AB}}+\Delta {\mathrm{U}}_{\mathrm{BC}}+\Delta {\mathrm{U}}_{\mathrm{CA}}=0\\ & \Delta {\mathrm{U}}_{\mathrm{CA}}=-\Delta {\mathrm{U}}_{\mathrm{AB}}-\Delta {\mathrm{U}}_{\mathrm{BC}}\\ & \Delta {\mathrm{U}}_{\mathrm{CA}}=-(-3)-(-5)=8\mathrm{kJ}/\mathrm{mol}\\ & \Delta {\mathrm{U}}_{\mathrm{CA}}={\mathrm{q}}_{\mathrm{CA}}+{\mathrm{W}}_{\mathrm{CA}}\\ & 8={\mathrm{q}}_{\mathrm{CA}}+3\\ & {\mathrm{q}}_{\mathrm{CA}}=+5\mathrm{kJ}/\mathrm{mol}\end{array}$ Heat absorbed has positive sign.