Question

The density of 2.0 M solution of a solute is 1.2 g `mL^(-1)`. If the molecular mass of the solute is 100 g `mol^(-1)`, then the molality of the solution is :
A. 2.0 m
B. 1.2 m
C. 0.6 m
D. 2.4 m.

Answer 1

Correct Answer - a
Volume of solution containing 2 moles of solute =1L =1000 mL
mass of solution =`Vxxd`
=`1000mL xx1.2 g mL^(-1)=1200 g`
Molality of solvent =1000 g=1.0 kg.
`"Molality of solution (m)"=("No. of moles of colute")/("Mass of solvent in kg")`
`=((2 moles))/(1 kg)=2 "mol kg"^(-1)=2.0 m`