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BCECE Engineering BCECE Engineering Solved Paper-2013

  • question_answer
    2.56 g of sulphur in 100 g of \[\text{C}{{\text{S}}_{\text{2}}}\]has depression in freezing point of \[0.010{{\,}^{o}}C.\] Atomicity of sulphur in \[C{{S}_{2}}\]is (Given,\[K{{}_{f}}={{0.1}^{o}}\,\text{mola}{{\text{l}}^{-1}}\])

    A) 2            

    B)                        4                             

    C) 6                     

    D) 8

    Correct Answer: D

    Solution :

    Let atomicity of sulphur is n, then it exists as \[{{S}_{n}}.\] \[\therefore \]Molar mass, \[m=32\,n\] Now from,  \[\Delta {{\Tau }_{f}}=\frac{1000w{{K}_{f}}}{m\,w}\]                 \[0.010=\frac{1000\times 2.56\times 0.1}{m\times 100}\]                 or            \[m=\frac{1000\times 2.56\times 0.1}{0.010\times 100}=256\]                 or            \[32\,n=256\]                 or,          \[n=\frac{256}{32}=8\]


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