what is the answer?

Question

If a system has 375 kcal of work done to it, and releases 5.00×102 kJ of heat into its surroundings, what is the change in internal energy (Δ𝐸 or Δ𝑈) of the system?

Δ𝐸=

Answer 1

So, if you didn't think my response was correct the last time you asked this question, why not leave a comment and ask, or tell me what was wrong. Instead you post the same question again, and so I will answer it again. If you don't understand the approach, or if it is incorrect, please comment so that we both can learn something.

First, let's convert kcal to kJ so we can work in the same units (or you could convert kJ to kcal)

375 kcal x 4.184 kJ / kcal = 1569 kJ of work done on the system

5.00x10² kJ of heat released

∆U = ∆E = q + w

q = heat = -500 kJ (negative because heat is released)

w = +1569 kJ (positive because work is done ON the system)

∆U = ∆E = -500 + 1569 = +1069 kJ