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

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