[Timothy]

Please can someone help me with this question;

A sample of 4.50g of methane occupies 12.7 dm3 at 310 K. (a) Calculate the work done when the gas expands isothermally against a constant external pressure of 200 Torr until its volume has increased by 3.3dm3. (b) Calculate the work that would be done if the same expansion occurred reversibly.

Thanks

[rabolisk]

You are supposed to attempt the problem first.

[Timothy]

I have but I don't know where to start as there is no heat capacity given.

[rabolisk]

You don't need heat capacity.

Start with the very basic equation in thermodynamics, which is dU = dq + dw.
Think about the definition of work. There is one assumption you have to make in part b.