# Homework Help: What is the change in entropy ΔS of the gas?

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1. Dec 16, 2015

### kolua

1. The problem statement, all variables and given/known data
Two moles of an ideal gas undergo a reversible isothermal expansion from 3.37×10−2m3 to 4.29×10−2m3 at a temperature of 29.6 ∘C.

What is the change in entropy ΔS of the gas?

2. Relevant equations
pV=nRT

3. The attempt at a solution
W=∫V2V1pdV,

I don't know how to use this integral. And is it necessary to use this integral here? It seems like it is making the calculation more complicated than it should be. I have no other idea on how to approach this question. Please give me some hints!

2. Dec 16, 2015

### Staff: Mentor

Hint: In the integration, P=nRT/V

3. Dec 16, 2015

### Conformal Bear

You're on the right path. Note that the integral should be
$$\int_{V_{1}}^{V_{2}} \frac{PdV}{T}$$
Manipulate the integrand using the ideal gas equation of state to obtain an expression in terms of the variable of integration (i.e. the volume) and then do the integral.
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