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MDCAT Chemistry QUESTION #4378
Question 1
If $100\ kJ$ of heat is absorbed by the system and $40\ kJ$ of work is done on the system, what is the change in internal energy?
  • $-60\ kJ$
  • $+60\ kJ$
  • $-140\ kJ$
  • $+140\ kJ$✔️
Correct Answer Explanation
By the first law of thermodynamics: $\Delta U = q + w$. Heat absorbed by system: $q = +100\ kJ$. Work done ON the system: $w = +40\ kJ$. Therefore $\Delta U = 100 + 40 = +140\ kJ$.