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JCECE Medical JCECE Medical Solved Paper-2005

  • question_answer
    A solution of 4.5 g of a pure non-electrolyte in 100 g of water was found to freeze at \[\text{0}\text{.465}{{\,}^{\text{o}}}\text{C}\text{.}\] The molecular weight of the solute is closest to \[\text{(}{{\text{k}}_{f}}\text{=1}\text{.86):}\]

    A)  135.0         

    B)  172.0

    C)  90.0           

    D)  180.0

    Correct Answer: D

    Solution :

     Key Idea: \[\text{Mole}\,\text{mass}=\,\,\frac{1000\times {{k}_{f}}\times w}{\Delta {{\Tau }_{f}}\times W}\] Given       \[{{k}_{f}}=1.86\] \[w=\]mass of solute = 4.5 g \[W=\]mass of solvent \[=100\,g\] \[\Delta {{\Tau }_{f}}=\]Depression in freezing point = 0.465° C \[\therefore \]Molecular weight of solute \[=\frac{100\times 1.86\times 4.5}{0.465\times 100}\] \[=180\]


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