JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer A solution of sucrose (molar mass\[~=342gmo{{l}^{-1}})\] has been prepared by dissolving \[68.5\,\,g\] of sucrose in \[1000\,\,g\] of water. The freezing point of solution obtained will be (\[{{K}_{f}}\]for water\[=1.86\,\,K\,\,kg\,\,mo{{l}^{-1}})\]

    A) \[-{{0.570}^{o}}C\]                         

    B) \[-{{0.372}^{o}}C\]

    C) \[-{{0.520}^{o}}C\]                         

    D)  \[+{{0.372}^{o}}C\]

    Correct Answer: B

    Solution :

    \[\Delta {{T}_{f}}=\frac{1000\times {{K}_{f}}\times {{w}_{2}}}{{{M}_{2}}\times {{w}_{1}}}\]         \[=\frac{1000\times 1.86\times 68.5}{342\times 1000}={{0.372}^{o}}C\]                 \[\Delta {{T}_{f}}=T_{f}^{o}-\Delta {{T}_{f}}=0-0.372={{0.372}^{o}}C\]

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