Question Detail
Question
What is the change in internal energy, ΔU, of a system that releases 20.4 kJ of heat and does 4.2 kJ of work on the surroundings?
Correct Answer
Option A is the correct answer.
Detailed Explanation
ΔU = q + w. q = -20.4 kJ (released, so negative), w = -4.2 kJ (work done by system on surroundings, so negative). ΔU = -20.4 + (-4.2) = -24.6 kJ.
Hint
Use the sign convention: heat absorbed by system is +, work done on system is +.