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Homework Statement
I am to show that ΔS=Q/T for the isothermal expansion of a monoatomic ideal gas, when the expansion is so slow that the gas is always in equilibrium.
Homework Equations
1. law: ΔU=Q+W (We mustn't use dQ and dW - our teacher hates that :( ).
Ideal gas law: PV=NkT
We need the equation: ΔS=Nk*ln(V_final/V_initial)
And that quasistatic expansion work is W=-PΔV
The Attempt at a Solution
-I think I am to start with: ΔU=Q+W⇔Q=ΔU-W, where ΔU=0 since its isothermal.
-I know that it is quasistatic expansion work, so W = -PΔV, so Q = -(-PΔV) = PΔV
I think I want to get something from the ideal gas law in here: P=(NkT)/V, so
Q=(NkTΔV)/V
But then I kind of get stuck there...
Hope someone can help. I thinks it is really easy, but I kind wrap my head around it.
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