Calculate the value of ΔE in joules for a system that loses 115 J of heat and has 150 J of work performed on it by the surroundings.
A)-115 J
B)-35 J
C)+35 J
D)+265 J
E)-265 J

Question

Quizplus · Accepted Answer

According to the first law of thermodynamics, the change in internal energy (ΔE) of a system is equal to the heat (q) added to the system minus the work (w) done by the system:

ΔE = q - w

In this problem, the system loses 115 J of heat, which means q = -115 J, and has 150 J of work performed on it by the surroundings, which means w = -150 J (since work done on the system is negative). Therefore,

ΔE = -115 J - (-150 J) = 35 J

The positive value of ΔE indicates that the internal energy of the system has increased. So, the correct answer is (C) +35 J.

Calculate the Value of ΔE in Joules for a System