Work formula Done by system vs on sytem
Started by JohnTulisa
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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
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
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
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