VMMC VMMC Medical Solved Paper-2013

  • question_answer
    For    the    following    equilibrium, \[{{N}_{2}}{{O}_{4}}2N{{O}_{2}};{{K}_{c}}=0.67.\]If we start with 3 moles of \[N{{O}_{2}}\]and 1 mole of \[{{N}_{2}}{{O}_{4}}\]in 1L flask, then \[N{{O}_{2}}\]present at equilibrium is

    A)  1.5 mol            

    B)  2.0 mol

    C)  0.5 mol            

    D)  1.0 mol

    Correct Answer: B

    Solution :

     \[{{N}_{2}}{{O}_{4}}(g)\rightleftharpoons 2N{{O}_{2}}(g)\] \[Q=\frac{{{[N{{O}_{2}}]}^{2}}}{[{{N}_{2}}{{O}_{4}}]}=\frac{{{[3]}^{2}}}{[1]}=9>{{K}_{c}}\] Thus, equilibrium is displaced in backward side. \[\underset{\begin{smallmatrix}  3 \\  (3-2x) \end{smallmatrix}}{\mathop{2N{{O}_{2}}}}\,\rightleftharpoons \underset{\begin{smallmatrix}  \,\,\,1 \\  (1+x) \end{smallmatrix}}{\mathop{{{N}_{2}}{{O}_{4}}}}\,\] \[K{{}_{c}}=\frac{1}{{{K}_{c}}}=\frac{1}{0.67}=\frac{1+x}{{{(3-2x)}^{2}}}=1.5\] Only permissible value of x that satisfies above equation is \[x=0.5\]Thus, \[N{{O}_{2}}\]at equilibrium \[=3-2x=2\,mol.\]


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