Q.

Sea water contains 29.25% NaCl and 19% MgCl2 by weight of solution. The normal boiling point of the sea water is ______ °C (Nearest integer)

Assume 100% ionization for both NaCl and MgCl2

Given: Kb(H2O) = 0.52 K kg mol-1

Molar mass of NaCl and MgCl2 is 58.5 and 95 g mol-1 respectively.                   [2023]


Ans.

(116)

Total weight of solute in solution=29.25+19=48.25 gm

Total weight of solvent in solution=100-48.25=51.75 gm

So ΔTb=i×Kb×m=(i×m)×Kb

Mole of NaCl=29.2558.5=0.5

Mole of MgCl2=1995=0.2

ΔTb=(2×29.2558.5×100051.75+3×1995×100051.75)×0.52

ΔTb=16.075

ΔTb=(Tb)solution-(Tb)solvent

(Tb)solution=100+16.07

                    =116.07°C