$200 \mathrm{~mL}$ of an aqueous solution of a protein contains its $1.26 \mathrm{~g}$. The osmotic pressure…

$200 \mathrm{~mL}$ of an aqueous solution of a protein contains its $1.26 \mathrm{~g}$. The osmotic pressure of this solution at $300 \mathrm{~K}$ is found to be $2.57 \times 10^{-3}$ bar. The molar mass of protein will be
  1. $51022 \mathrm{~g} \mathrm{~mol}^{-1}$
  2. $122044 \mathrm{~g} \mathrm{~mol}^{-1}$
  3. $31011 \mathrm{~g} \mathrm{~mol}^{-1}$
  4. $61038 \mathrm{~g} \mathrm{~mol}^{-1}$

Solution

$\begin{aligned} & \because \pi=C R T \\ &=\frac{w \times 1000}{M \times V(\text { in mL })} \times R T \\ & \quad\left[\because C=\frac{n \times 1000}{V(\text { in mL })} \text { and } n=\frac{w}{M}\right] \\ &=\frac{1.26 \times 1000 \times 0.083 \times 300}{2.57 \times 10^{-3} \times 200} \\ &=61038 \mathrm{~g} \mathrm{~mol}^{-1} \end{aligned}$

Asked in: NEET 2011 (Mains)

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