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J & K CET Medical J & K - CET Medical Solved Paper-2009

  • question_answer
    25 g of a solute of molar mass\[250\text{ }g\text{ }mo{{l}^{-1}}\] is dissolved in 10 mL of water to obtain a solution whose density is\[1.25\text{ }g{{(mL)}^{-1}}\]. The molarity and molality of the solution are respectively

    A)  0.75 M and 1 m               

    B)  0.8 M and 1 m

    C)  1M and 0.8 m   

    D)  1 M and 0.75 m (e) None of the above

    Correct Answer: D

    Solution :

                    (*) Molarity \[=\frac{weight\text{ }of\text{ }solute\times 1000}{mol.\text{ }wt.\text{ }of\text{ }solute\times volume\text{ }of\text{ }solution}\] \[=\frac{25\times 1000}{250\times 1000}\][\[\because \]density of water\[=1\text{ }g\text{ }{{(mL)}^{-1}}\]] \[=1\,M\] \[Molality=\frac{weight\text{ }of\text{ }solute\times 1000}{mol.\text{ }wt.\text{ }of\text{ }solute\times wt.\text{ }of\text{ }solvent}\]                 \[=\frac{25\times 1000}{250\times 100}=1\,m.\]


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