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NEET Sample Paper NEET Sample Test Paper-70

  • question_answer
    Ionisation energy of \[\operatorname{Al}=5137\,kJ mol{{e}^{-}}^{1}\left( \Delta H \right)\] and hydration of \[A{{l}^{3+}}=\,\,-4665\,\,kJ\,\,mol{{e}^{-1}}\]. \[{{(\Delta H)}_{hydration}}\,\,for\,\,C{{l}^{-}}=-\,381\,\,kJ\,\,mole{{\,}^{-}}\,1\]. Which of the following statement is correct?

    A) \[AlC{{l}_{3}}\] would remain covalent in aqueous solution

    B) Only at infinite dilution \[AlC{{l}_{3}}\] undergoes ionisation

    C) In aqueous solution \[AlC{{l}_{3}}\] becomes ionic

    D) None of these

    Correct Answer: C

    Solution :

    If \[AlC{{l}_{3}}\] is present in ionic state in aqueous solution, therefore it has \[A{{l}^{3+}}\text{ }and\text{ }3C{{l}^{-}}\] ions Standard heat of hydration of \[A{{l}^{3+}}\text{ }and\text{ }3C{{l}^{-}}\] ions \[= \,- 4665 + 3 \times  \left( -381 \right) kJ mole{{\,}^{-}}^{1}\] \[\,= -5808 kJ/mole\] Required energy of ionisation of \[\operatorname{Al} = 5137 kJ mole{{\,}^{-}}^{1}\] \[\therefore \] Hydration energy overcomes ionisation energy \[\therefore \] \[AlC{{l}_{3}}\] would be ionic in aqueous solution


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