Q.

Molarity (M) of an aqueous solution containing x g of anhyd. CuSO4 in 500 mL solution at 32°C is 2×10-1 M. Its molality will be _____ ×10-3m. (nearest integer).

 

[Given density of the solution = 1.25 g/mL]                       [2024]


Ans.

(164)

                Wsolution=dsolution×Vsolution=1.25 gmL×500 mL=625 g

                nsolute=Molaritysolution×Vsolution=2×10-1 M×0.5 L=0.1 mol

               Wsolute=nsolute×molar mass of solute=0.1 mol×159.5 gmol-1=15.95 g

              Wsolvent=Wsolution-Wsolute=625 g-15.95 g=609.05 g

              m=nsolute×1000Wsolvent (in g)=0.1×1000609.05m=0.1642 m=164×10-3 m