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KVPY Sample Paper KVPY Stream-SX Model Paper-4

  • question_answer
    Element A burns in nitrogen to give an ionic compound B. Compound B reacts with water to give C and D. A solution of C becomes 'milky' on bubbling carbon dioxide. The element A is

    A) \[Na\]                           

    B) \[Mg\]

    C) \[Ca\]               

    D) \[Be\]

    Correct Answer: C

    Solution :

    [c] \[\underset{A}{\mathop{3M}}\,+{{N}_{2}}\xrightarrow{{}}\underset{B}{\mathop{{{M}_{3}}{{N}_{2}}}}\,\] \[\underset{B}{\mathop{{{M}_{3}}{{N}_{2}}}}\,+6{{H}_{2}}O\xrightarrow{{}}\underset{C}{\mathop{3M{{(OH)}_{2}}}}\,+\underset{D}{\mathop{2N{{H}_{3}}}}\,\] \[\underset{C}{\mathop{M{{(OH)}_{2}}}}\,+C{{O}_{2}}\xrightarrow{{}}\underset{D}{\mathop{MC{{O}_{3}}}}\,+{{H}_{2}}O\] M may be either \[Ca\] or Ba. It is not magnesium because \[Mg{{(OH)}_{2}}\] has very low solubility in water. Thus, the correct option is [c].        


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