Question

An aqueous solution containing $\mathrm{21.6.}mg$ at solute in $100ml$ of solution had an asmotic pressure of $3.70m$of Hg at ${25}^{o}C$.The molecular wt of solution in $g.mol$ is

• A. $1085$
• B. $9035$
• C. $1355$
• D. $700$

Answer 1

Answer: (A)

$1085$

$3.7$ $m=3700$ $mm$
Osmotic pressure $=CRT$
$⟹Pressure=\left(\frac{3.7mm}{760mm}\right)$ $atm$
$⟹\left(\frac{3.7}{760}\right)\times {10}^3=(\frac{21.6\times {10}^{-3}}{\left(M\right)}\times \frac{1000}{100})\times \left(0.0821\right)\left(298K\right)$
$⟹M=\frac{\left(760\right)}{3.7\times {10}^3}\times 21.6\times {10}^{-2}\times \left(0.0821\right)298$
Molecular weight $=1085.48$ $g$