RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    The boiling point of water is\[{{100}^{o}}C\]. What will be the boiling point of an aqueous solution containing \[0.6\,\,g\] of urea (molar mass\[=60\]) in \[100\,\,g\] of water?(\[{{K}_{b}}\]for water\[=0.52\,\,K/m\])

    A) \[{{100.052}^{o}}C\]                      

    B)        \[{{101.052}^{o}}C\]

    C)        \[{{120.52}^{o}}C\]                         

    D)         None of these

    Correct Answer: A

    Solution :

    We know that,                 \[\Delta {{T}_{b}}=\frac{{{K}_{b}}\times {{w}_{B}}\times 1000}{{{M}_{B}}\times {{w}_{A}}}\]                 \[{{K}_{b}}=0.52K\,\,{{m}^{-1}},\,\,{{w}_{B}}=0.6\,\,g,\,\,{{M}_{b}}=60\]                 \[{{w}_{A}}=100\,\,g\] \[\therefore \]  \[\Delta {{T}_{b}}=\frac{0.52\times 0.6\times 1000}{60\times 1000}={{0.052}^{o}}C\] Thus boiling point of the solution                        \[=100+0.052={{100.052}^{o}}C\]


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