The density of 2.0 M solution of solute is 1.2 gm/ml. If the molecular mass of solute is 100 gm `"mol"^(-1)` then the molality of the solution is

Options

A. 2.0 m
B. 1.2 m
C. 1.0 m
D. 0.6 m

Answer

A

Explanation

Hint: denisty `=m/v ` or M = density `xxV`
`1.2 xx1000 = 1200, g M_B = 100`
`N_B = W_B/M_B`
or `W_B = 2 xx100 = 200 ` gm
Weight of solvent `=1200 - 200 = 1000`
`m= N_B xx(1000)/W_A= 2 xx 1000/1000`
m = 2m