Question

Insulin is dissolved in a suitable solvent and the osmotic pressure ($\pi$) of solutions of various concentrations ($g/c{m}^3$) C is measured at ${27}^{0}C$. The slope of the plot of $\pi$ against C is found to be $4.1\times {10}^{-3}$. The molecular mass of inulin is :

• A. $6\times {10}^6$
• B. $3\times {10}^6$
• C. $6\times {10}^3$
• D. $3\times {10}^3$

Answer 1

The correct option is A $6\times {10}^6$

Given that,

Slope, $m=4.1\times {10}^{-3}=\frac{\pi }{C}$

Now,

$\pi =\frac{w\times R\times T}{V\times M}=C\frac{RT}{M}$

$\Rightarrow M=\frac{CRT}{\pi }=\frac{RT}{m}=\frac{0.0821\times 300\times 1000}{4.1\times {10}^{-3}}=6\times {10}^{6}g$

Note: Multiply by 1000 since volume is in cm${}^3$.