CMC Medical CMC-Medical VELLORE Solved Paper-2009

  • question_answer
    Correct order of freezing point of 1 M solution of sucrose, \[KCl,\]\[BaC{{l}_{2}}\] and \[AlC{{l}_{3}}\]is

    A)  Sucrose \[>KCl>BaC{{l}_{2}}>AlC{{l}_{3}}\]

    B)  \[AlC{{l}_{3}}>BaC{{l}_{2}}>KCl>\] Sucrose

    C)  \[BaC{{l}_{2}}>KCl>AlC{{l}_{3}}>\] Sucrose

    D)  \[KCl>BaC{{l}_{2}}>AlC{{l}_{3}}>\]Sucrose

    Correct Answer: A

    Solution :

                                    Depression in freezing point is a colligative property, it means that as the number of particles (ions) of solute increases, freezing point of the solution decreases. Sucrose \[\xrightarrow{{}}\]not ionised \[KCl\rightleftharpoons \underbrace{{{K}^{+}}+C{{l}^{-}}}_{2\,\,ions}\] \[BaC{{l}_{2}}\rightleftharpoons \underbrace{B{{a}^{2+}}+2C{{l}^{-}}}_{3\,\,ions}\] \[AlC{{l}_{2}}\rightleftharpoons \underbrace{A{{l}^{3+}}+3C{{l}^{-}}}_{4\,\,ions}\] Hence, the correct order of freezing point is Sucrose \[>KCl>BaC{{l}_{2}}>AlC{{l}_{3}}\]


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