question_answer

\[\underset{\begin{smallmatrix}  Gives\,\,crimson\,\,red \\  flame\,\,colour \end{smallmatrix}}{\mathop{Metal\,(A)}}\,\xrightarrow{air(\Delta )}(B)\xrightarrow{{{H}_{2}}O}Hydroxides\,\,of\,\,(A)+C(gas)\]\[C(gas)\xrightarrow[{{K}_{2}}[Hg{{I}_{4}}]+NaOH]{}Brown\,\,ppt.\] Identify species A, B and C.

A)                                 A - \[Mg\]           B - \[M{{g}_{3}}{{N}_{2}}\]    C - \[N{{H}_{3}}\]

B) A - \[Li\]            B - \[L{{i}_{3}}N\]        C - \[N{{H}_{3}}\]

C) A - \[Li\]            B - \[L{{i}_{2}}O\]        C - \[N{{O}_{2}}\]

D) A - \[Mg\]           B - \[MgO\]        C - \[N{{O}_{2}}\]

Correct Answer: B

Solution :

[b] In alkali metals only \[Li\]forms nitrides \[(L{{i}_{3}}N)\] with \[{{N}_{2}}\] (from air) whereas all alkaline earth metals forms nitrides (M N ). But \[Li\]gives crimson red flame colour whereas \[Be\]and \[Mg\]do not impart flame colour thus metal [a] is\[Li\]. Iodide of millon's base (Brown ppt)