AMU Medical AMU Solved Paper-2000

  • question_answer
    The freezing points of equimolar solutions of glucose, \[KN{{O}_{3}}\] and \[AlC{{l}_{3}}\] are in the order of

    A)  \[AlC{{l}_{3}}<\] glucose \[<KN{{O}_{3}}\]

    B)  \[AlC{{l}_{3}}<KN{{O}_{3}}<\] glucose

    C)  glucose \[<KN{{O}_{3}}<AlC{{l}_{3}}\]

    D)  glucose \[<AlC{{l}_{3}}<KN{{O}_{3}}\]

    Correct Answer: B

    Solution :

                     Key Idea             \[T={{T}_{0}}-(\Delta {{T}_{f}})\] where, \[{{T}_{0}}\] is freezing temperature of solvent \[\Delta {{T}_{f}}=i\times {{K}_{f}}\times m\] where, m is molality, \[{{K}_{f}}\] is molal depression constant                 i = vant Hoff factor                 \[i=[1+(y-1)\,x]\] where y = number of products (ion or molecule) obtained per mole of the reactant. Here the solutions are equimolar. So, \[\Delta {{T}_{f}}\]depend upon i.
    Solute Ionisation product Y \[i=[1+(y-1)x]\]her , \[x=1\]
    Glucose No (it is non-electrolvte) 1 1
    \[KN{{O}_{3}}\] \[{{K}^{+}}+NO_{3}^{-}\] 2 2
    \[AlC{{l}_{3}}\] \[A{{l}^{3+}}+3C{{l}^{-}}\] 4 4
    Greater the value of i, greater the value of \[\Delta {{T}_{f}}\] but smaller the value of freezing point. Therefore, the freezing points of equimolar solutions of glucose, \[KN{{O}_{3}}\] and \[AlC{{l}_{3}}\] are in the order of \[AlC{{l}_{3}}<KN{{O}_{3}}<\] glucose


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