## 7th Edition, 4.B.13

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Ahmed Mahmood 4D
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Joined: Fri Sep 28, 2018 12:28 am

### 7th Edition, 4.B.13

The question asks you to calculate an irreversible expansion from 4.52 L to 6.52 L under constant external pressure of 1.00 atm for part a. The answer to this should be 2.23, as the change in volume is 2.23 L and the pressure is constant, but the book puts it as 226 J. Why?

Chem_Mod
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### Re: 7th Edition, 4.B.13

When the pressure is constant the work does not equal the change in volume. The equation for an irreversible expansion is W=-nRTln(V2/V1).

Timothy_Yueh_4L
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### Re: 7th Edition, 4.B.13

I believe the question is asking for the work done by irreversible expansion in which case is found using the equation W = P*delta(V). We multiply delta(V), 2.23L, with the constant external pressure, 1 atm, and get 2.23 L*atm which being a unit of energy is not in its standard form joules. To convert it to joules we multiply the value by the conversion factor 101.325J/(L*atm) and receive 226J.