2.17 The vapour pressure of water is at Calculate vapour pressure of 1 molal solution of a non-volatile solute in it.
It is asked the vapour pressure of 1 molal solution which means 1 mol of solute in 1000 g H2O.
Moles in 1000g of water = 55.55 mol. (Since the molecular weight of H2O is 18)
Mole fraction of solute :
Applying the equation :
Thus the vapour pressure of the solution is 12.083 KPa