Question

​the internal energy of the system is increased by 400 kj while the system performs 125 kj of work on the surroundings. how much heat was transferred by between the system and its surroundings during this process? in what direction did the heat flow?

Answer 1

Dear Student,

$$\begin{gathered} ∆\mathrm{E}=400\mathrm{kJ} \\ \mathrm{W}=-125\mathrm{kJ} \\ \mathrm{We}\mathrm{know}\mathrm{that}, \\ ∆\mathrm{E}=\mathrm{q}+\mathrm{W} \\ 400=\mathrm{q}-125\mathrm{kJ} \\ \mathrm{or},\mathrm{q}=400+125=525\mathrm{kJ} \\ \mathrm{Since}\mathrm{q}=+\mathrm{ve},\mathrm{this}\mathrm{means}\mathrm{heat}\mathrm{is}\mathrm{added}\mathrm{to}\mathrm{the}\mathrm{system}. \end{gathered}$$