# Thermodynamics – Ideal gas expansion

**1. The problem statement, all variables and given/known data**

2.1E5 J of heat enters an ideal gas as it expands at a constant T = 77°C to four times its initial volume. How many moles of gas are there?

T=350K, Q=2.1E5 J, Vi=x, Vf=4x

**2. Relevant equations**

ΔU=Q-W

W=[itex]\int[/itex]pdV

U=nCvT

**3. The attempt at a solution**

I’m not sure if I’m even on the right track here.

I have W=[itex]\int[/itex]pdV = nRT[itex]\int[/itex]dv/V = nRTln(Vf-Vi)

I am stuck here because I need to know n to solve for work but I need to know W to solve for n. I am clearly missing something but I can’t figure out what it is.

http://ift.tt/1kOYdef

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