Question

A solution weighing $a$ gram has molality $b$. The molecular mass of solute if the mass of solute is $c$ gram, will be:

• A. $\frac{c}{b}\times \frac{1000}{(a-c)}$
• B. $\frac{b}{a}\times \frac{1000}{(a-b)}$
• C. $\frac{b}{c}\times \frac{1000}{(a-c)}$
• D. $\frac{c}{a}\times \frac{1000}{(b-a)}$

Answer 1

The correct option is A $\frac{c}{b}\times \frac{1000}{(a-c)}$

$Molality=\frac{W_{solute}}{M\cdot wt}\times \frac{1000}{W_{solvent}\left(inKg\right)}$

$b=\frac{c}{M\cdot wt}\times \frac{1000}{(a-c)}$

$M\cdot wt=\frac{c}{b}\times \frac{1000}{a-c}$