Question

(a) A certain mass of gas initially at `(1L, 5 atm, 300 K)` is expanded reversible and isothermally to final volume of `5L`, calculate the work done by the gas and heat supplied in this process to the gas.
(b) Now, if the gas is released to initial position by compressing it using an external constant pressure of `5` atm. Fins work done on the gas in this process and heat rejected by gas
(c ) In the above two processes, what is the net gained by surroundings ?
[Note: From above question see that surrounding has done extra work on the system but system has returned that work in the form of heat to surrounding and work is considered on organized form of energy while heat as an unorganised form hence in the above process, there must be net increment in randomness of universe which be called Entropy, soon]

Answer 1

`PV=nRT " " rArr5xx1=nxx0.82xx300 " "rArrn=0.203`
(a) `{:("Initial",,,,"Final"),(V=1L,,,,V_(2)=5L),(P=5atm,,,,),(T=300K,,,,T=300K):}`
`w= -2.303 nRT "log "(V_(2))/(V_(1))= -2.303xx0.203xx8.314xx300 log 5= -816J`
`w= -816J` and `q= -w=816 J`
So, work done by the gas `=816 J`
(b) `w= -P_(ext)(V_(2)-V_(1))= -5[1.5]= +20xx101.325`
`w=2026 J`
(c ) `q_(1)= -w_(1)= +816 J`
`q_(2)= -w_(2)= -2026 J`
`q_(1)+q_(2)= -1210 J`
So, Net heat released by the system `= -1210`