Work formula Done by system vs on sytem

[JohnTulisa]

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For this question, work is done ON the system.
We utilize the formula W = -PV
If the question changes the condition to work is done BY the system, do we change the formula to W= PV or keep it as W = - PV?

 

[Mrhyde]

My understanding is this: the system doing work on the surroundings is Exothermic also known as a compression ( so negative sign) .... The surroundings doing work on the system is Endothermic ( so positive sign) also know as an expansion

 

[Lnguyen7]

Work = -PΔV = -P(Vf - Vi) regardless. What important is

1. If work done by the system on surrounding or gas expansion ΔV > 0, so -PΔV < 0
2. If work done by the surrounding on system or gas compression ΔV < 0, so -PΔV > 0

Ex 1: if a gas expands from 16 L to 40 L at a constant pressure of 4.0 atm...
Work = -PΔV = -4.0(40 - 16) = -96 J

Not
Work = PΔV = 4.0(40 - 16) = 96 J

Ex 2: if the work done by compression of a gas is 50 J then W = -50J