Question

A compound $H_{2}X$ with molar weight of 80 g is dissolved in a solvent having density of 0.4 g $m{L}^{-1}.$ Assuming no change in volume upon dissolution, the molality of a 3.2 molar solution is ___

Answer 1

PLAN This problem can be solved by using concept of conversion of molarity into molality
Molarity = 3.2 M
Let volume of solution = 1000 mL = Volume of solvent
Mass of solvent = 1000 $\times$ 0.4 = 400 g
Since, molarity of solution is 3.2 molar
$\therefore n_{solute}$ = 3.2 mol
Molality (m) = $\frac{3.2}{100/1000}=8$
Hence, correct integer is (8).