Calculate the entropy increase in the evaporation of 1 mole of a liquid when it boils at 100 degree centigrade having heat of vaporisation at 100 degree as 540cals\gm

Answer 1

I don't think you have enough information.
dG = dH - TdS
At boiling, dG = 0
Then TdS = dH and
dS = dH/T = 540/373 but that gives you cal/g and you want cal/mol. Without knowing the molar mass (I assume this is water but the problem doesn't say that), I can't convert from cal/gram to cal/mol.

Answer 2

26calk/mol