Suppose you do 75 kJ of work on a system consisting of 10 kg of water by stirring it with a paddle wheel. During this process, 40 kcal of heat is removed. The change in the internal energy of the system is
A) -92 kJ.
B) -115 kJ.
C) -134 kJ.
D) -242 kJ.
E) -156 kJ.

Question

Quizplus · Accepted Answer

The change in internal energy is given by the first law of thermodynamics:ΔU = Q - Wwhere ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done on the system.In this case, Q = -40 kcal = -167 kJ and W = 75 kJ. Therefore,ΔU = -167 kJ - 75 kJ = -242 kJThe correct answer is A.

Suppose You Do 75 KJ of Work on a System