[coolnerd]

Expansion irreversibly and isothermally of an ideal has from a volume of 2dm3 to 10 dm3 against a const pressure of 1 atm at 27 C .Find entropy change of the system and also surroundings due to the process.

Heres my attempt:
delta S=energy absorbed/temp
for the system,
= energy absorbed/temp=RTln(V2/V1)/T(as it is an isothermal exp)
putting in values I got,13.4J/K/mol
since energy absorbed by surroundings= -(energy absorbed by system)
delta S of surroundings= -13.4J/K/mol
My book gives different answer fro 2nd part.
Why am I wrong?
I just don't understand when we have to consider work and when not?(like for the system or the surroundings?)

[rabolisk]

This is clearly not high school chemistry, but most likely a pchem course. I would start with the definition of entropy as the reversible heat / temperature.

[coolnerd]

hi.I couldn't find a pre university forum.
I did use the definition of entropy didn't I?

[Jesse2024]

Firstly you need to realise that we are dealing with an irreversible process, meaning  :delta: S > q/T

[coolnerd]

alright can you point out where I am wrong(I have used that).