NEET Sample Paper NEET Sample Test Paper-93

  • question_answer
    Sodium Carbonate cannot be used in place of \[{{(N{{H}_{4}})}_{2}}C{{O}_{3}}\] for the identification of \[C{{a}^{2+}},\]\[B{{a}^{2+}}\] and \[S{{r}^{2+}}\]ions (in group V) during mixture analysis because :

    A) \[M{{g}^{2+}}\] ions will also be precipitated.

    B) Concentration of\[C{{O}_{3}}^{2-}\] ions is very low.

    C) Sodium ions will react with acid radicals.

    D) \[N{{a}^{+}}\] ions will interfere with the detection of \[C{{a}^{2+}},\]\[B{{a}^{2+}},\]\[S{{r}^{2+}}\] ions.

    Correct Answer: A

    Solution :

    [a] If \[N{{a}_{2}}C{{O}_{3}}\]is used in place of \[{{(N{{H}_{4}})}_{2}}C{{O}_{3}}.\]It will precipitate group V radicals as well as magnesium radicals. The reason for this is the high ionization of \[N{{a}_{2}}C{{O}_{3}}\] in water into \[-N{{H}_{2}}\] and \[CO_{3}^{2-}.\] Now the higher concentration of\[CO_{3}^{2-}\] is available which exceeds the solubility product of group V radicals as well as that of magnesium radicals.


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