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AIIMS AIIMS Solved Paper-2001

  • question_answer
    20 g of a substance were dissolved in 500 mL of water and the osmotic pressure I of the solution was found to be 600 mm of mercury at \[{{15}^{o}}C\]. The molecular weight of substance is:

    A)  998                       

    B)         1028     

    C)                         1098                     

    D)         1198

    Correct Answer: D

    Solution :

    According to vant Hoffs solution equation \[\pi V=nRT\] or        \[\pi V=\frac{w}{m}RT\] \[\pi \] (osmotic pressure) \[=600mm=\frac{600}{760}atm\] \[w=20\text{ }g;\text{ }R=0.0821\text{ }L\text{ }atm\text{ }mo{{l}^{-1}}\text{ }{{K}^{-1}}\] \[T=273+15=288\text{ }K\] \[V=500mL=0.5L\] \[m=\frac{wRT}{\pi V}\] \[=\frac{20\times 0.0821\times 288\times 760}{600\times 0.5}=1198.0\]


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