Two litres of an ideal gas at a pressure of 10 atm expands isothermally into vacuum until its total volume is 10 litres. How much heat is absorbed an how much work is done in the expansion? What would be the heat absorbed and work done
(i) If the same expansion takes place against a constant external pressure of 1 atm?
(ii) If the same expansion takes place to a final volume of 10 litres conducted reversibly?
For isothermal expansion of an ideal gas ΔU = 0
∴ q = −w = Pex (10L − 2L) = 0(8) = 0
(i) q = −w = 1 atm × 8L = litre atm
(ii) q = −w = 2.303 RT log V2/V1 = 2.303 PV log V2/V1= 2.303 × 10 atm × 2L log 10/2 = 32.2 L atm.