For a sample of perfect gas when its pressure is changed isothermally form p_(i) to p_(p) the entropy change is given by

For a sample of perfect gas when its pressure is changed isothermally

1.	For a sample of perfect gas when its pressure is changed isothermally form p_(i) to p_(p) the entropy change is given by
Answer» `DeltaS = nR in ((p_(f))/(p_(i)))` `DeltaS = nR in ((p_(i))/(p_(f)))` `DeltaS = nRT in ((p_(f))/(p_(i)))` `DeltaS = nRT in ((p_(i))/(p_(f)))` Solution :For an ideal gas UNDERGOING reversible expansion when temperature changes from `T_(i) `to `T_(f)` and pressure changes from `p_(i)` to `p_(f)` `DeltaS = nC_(p) In((T_(f))/(T_(i))) + nR"In((p_(i))/(p_(f)))` SINCE the process is isothermal , `T_(i) = T_(f)` and In 1 = 0 `THEREFORE DeltaS = nR"In ((p_(i))/(p_(f)))`