00:01
Dear students, as per the question, a quantity of an ideal gas in an isolated system expands isothermally and reversibly at 400 kelvin from a volume v1 to volume v2.
00:15
During expansion, the gas absorbs 200 joule of heat from the reservoir.
00:22
Suppose the gas expands volume v1 to volume v2 isothermally but irreversibly at 400 degree kelvin, it absorbs 100 joule of heat.
00:34
Then so when there is reversible absorption or expansion, it absorbs 200 joule of heat and when there is irreversible isothermal expansion, it absorbs 100 joule.
00:46
This you have to remember.
00:48
Now the first question is the entropy change of the gas.
00:51
So here there are two processes are given in the question.
00:55
Then for the first reversible process, for reversible it is entropy change, entropy change equal to s equal to entropy change is s equal to q divided by t.
01:18
So q is heat absorbed is 200 joule at temperature 400 kelvin.
01:24
So it is 0 .5 joule per kelvin...