NEET AIPMT SOLVED PAPER 2003

  • question_answer
                    The following equilibria are given:                                                                                                                   \[\begin{matrix}    {{N}_{2}}+3{{H}_{2}}2N{{H}_{3}} & {{K}_{1}}  \\ \end{matrix}\]                 \[\begin{matrix}    {{N}_{2}}+{{O}_{2}}2NO & {{K}_{2}}  \\ \end{matrix}\]                 \[\begin{matrix}    {{H}_{2}}+\frac{1}{2}{{O}_{2}}{{H}_{2}}O & {{K}_{3}}  \\ \end{matrix}\]                      The equilibrium constant of the reaction \[2N{{H}_{3}}+\frac{5}{2}{{O}_{2}}\rightleftharpoons 2NO+3{{H}_{2}}O\] in terms of \[{{K}_{1}},\,{{K}_{2}}\] and \[{{K}_{3}}\] is:

    A)                 \[\frac{{{K}_{1}}K_{3}^{2}}{{{K}_{2}}}\]                            

    B)                 \[\frac{{{K}_{2}}\,K_{3}^{3}}{{{K}_{1}}}\]         

    C)                 \[{{K}_{1}}\,{{K}_{2}}\,{{K}_{3}}\]       

    D)                 \[\frac{{{K}_{1}}\,{{K}_{2}}}{{{K}_{3}}}\]

    Correct Answer: B

    Solution :

                    For equilibrium                 \[{{N}_{2}}(g)+3{{H}_{2}}(g)2N{{H}_{3}}(g)\],\[{{K}_{1}}=\frac{{{[N{{H}_{3}}]}^{2}}}{[{{N}_{2}}]{{[{{H}_{2}}]}^{3}}}\]            ?(i)                 \[{{N}_{2}}(g)+{{O}_{2}}(g)\rightleftharpoons 2NO(g),\]\[{{K}_{2}}=\frac{{{[NO]}^{2}}}{[{{N}_{2}}]\,[{{O}_{2}}]}\]                              \[.....(ii)\]                 \[{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\rightleftharpoons {{H}_{2}}O(g),\]\[{{K}_{3}}=\frac{[{{H}_{2}}O]}{[{{H}_{2}}]\,{{[{{O}_{2}}]}^{1/2}}}.....(iii)\]                 For reaction,                   \[2N{{H}_{3}}(g)+\frac{5}{2}{{O}_{2}}(g)\rightleftharpoons 2NO(g)+3{{H}_{2}}O(g)\]                 \[K=\frac{{{[NO]}^{2}}\times {{[{{H}_{2}}O]}^{3}}}{{{[N{{H}_{3}}]}^{2}}\,{{[{{O}_{2}}]}^{5/2}}}....(iv)\]                 From equations number (i), (ii) and (ii)                 \[K=\frac{{{K}_{2}}\times {{K}_{3}}^{3}}{{{K}_{1}}}\]


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