Chemistry Question

Question

If a system has 5.00×10^2 kcal of work done to it, and releases 5.00×10^2 kJ of heat into its surroundings, what is the change in internal energy (Δ𝐸 or Δ𝑈) of the system?

Answer 1

Let's first get our units the same. I'll convert cal to J

5.00x10² kcal x 4.184 kJ/kcal = 209 kJ

∆U = q + w

q = heat = -5.00x10² kJ (minus because heat was RELEASED)

w = work = +209 kJ (positive because work was done ON the system)

∆U = -500 kJ + 209 kJ

∆U = -291 J