physical CHEM

Vapour pressure depends on mole fraction of solute...
More solute ==> less vapour pressure (rel. lowering of VP)

Now solubility = 36gm/100gm

if there is more salt then it will not get dissolved and hence due to the excess salt vapour pressure will not get reduced as lowering of VP takes place due to SOLUTION only.. So

VP of I = VP of II bcz. both save same mole fraction of solute in SOLUTION ...

and mole fraction of NaCl in III is less in III so less solute ==> more vapour pressure

SO I=II<III

mole fraction of solute in solution

in case I the remaining 4gm/100gm of solute is not dissolved and remains deposited at the bottom. hence it has no contribution towards lowering of vapour pressure