different ways to calculate w

[Chew 2H]

when do we use -PdeltaV and when do we use -nRTln(V2/V1) in calculating w? What's the difference between the two?

[Farah Ahmad 2A]

Generally you would use w=-nrtln(v2/v1) when it is an isothermal, reversible reaction.

[Abigail Yap 2K]

Hi,

I believe the first equation is used when the system is at equilibrium (constant pressure) and the second is used when the pressure is changing.

[Luis De La Cruz 1H]

Indeed, you would use the first equation for instances in which pressure is constant, since the equation itself seems to tell you there is no change in pressure, only a change in volume, hence the missing delta before pressure. While the second equation is a derived equation (which you don't need to know the derivation of) that is used for instances in which pressure is not maintained at a constant.

[AtreyiMitra2L]

We use the former with constant pressure and the latter when its not constant pressure. The first is irreversible expansion and the latter is irreversible, isothermal expansion.