Eternal Pressure Acting on a System

Question

What is the external pressure acting on a system that expands from 10 L to 25 L and does 210 L atm of work to the surroundings?

Answer 1

Since there is expansion, this means the system is doing work on the surrounding, making the sign of work (w) negative. The change in volume (∆V) is positive.

w = -P∆V

-210 L-atm = -P x 15 L

-210 L-atm/15 L = -P

P = 14 atm