Asample of 4.50 g 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 3.3 dm3. (b) calculate the work that would be done if the same expansion occurred reversibly.

(A) Work done will be 87.992 KJ

(B) Work done will be 167.4 KJ            

Explanation:

We have given mass of methane m = 4.5 gram = 0.0045 kg

Volume occupies

And volume is increased by so

Temperature T = 310 K

Pressure is given as 200 Torr = 26664.5 Pa

(a) At constant pressure work done is given by

(b) At reversible process work done is given by

We have given mass = 4.5 gram

Molar mass of methane = 16

So number of moles

So work done