30Swordfish.. Nowhere is it mentioned that it is a reversible process. So the formula for work done is redundant.
For irreversible process,
W=-PextΔV
so, ΔE= q - PextΔV
1It is given that 'at the same temperature' (in the question).
So conclusion is that it is an isothermal process.
Why can't we apply W=nRTln(V2/V1)?
30
Ashish Kothari
·2010-10-19 22:36:29
See, there's no doubt that it is an isothermal process. But, if you look carefully at the question, it is implied that is an irreversible process. Because see, they have mentioned that the process takes place at constant pressure of 1atm. In a reversible process, at every step internal and external pressure are at equilibrium. So, the given process cannot be reversible. And the formula for work done, W=nRTln(V2/V1) can be applied only for reversible process.
Thats why the difference in answer!
1
swordfish
·2010-10-20 06:09:18
Thanks alot,
One thing- Evaporation of water is a reversible process. Moreover, evaporation takes place only when vapour pressure of water equalises the atmospheric pressure (or external pressure which is 1atm in this case). So the pressure of the system and surroundings is also in equilibrium.
PLease explain I am desperate.
