Some Basic Concepts of Chemistry 1 Question 20
41. A compound $\mathrm{H}_{2} X$ with molar weight of $80 \mathrm{~g}$ is dissolved in a solvent having density of $0.4 \mathrm{~g} \mathrm{~mL}^{-1}$. Assuming no change in volume upon dissolution, the molality of a 3.2 molar solution is
(2014 Adv.)
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Solution:
- PLAN This problem can be solved by using concept of conversion of molarity into molality.
Molarity $=3.2 \mathrm{M}$
Let volume of solution $=1000 \mathrm{~mL}=$ Volume of solvent
Mass of solvent $=1000 \times 0.4=400 \mathrm{~g}$
Since, molarity of solution is 3.2 molar
$$ \begin{aligned} n_{\text {solute }} & =3.2 \mathrm{~mol} \ \text { Molality }(m) & =\frac{3.2}{400 / 1000}=8 \end{aligned} $$
Hence, correct integer is (8).
