KVPY Sample Paper KVPY Stream-SX Model Paper-20

  • question_answer
    The value of \[{{\operatorname{K}}_{\rho }}\] for the equilibrium reaction
    \[{{N}_{2}}{{O}_{4}}(g)2N{{O}_{2}}(g)is2.\]
    The percentage dissociation of \[{{N}_{2}}{{O}_{4}}(g)\] at a pressure of 0.5 atm is

    A) 25

    B) 88

    C) 50        

    D) 71

    Correct Answer: D

    Solution :

    \[{{\operatorname{N}}_{2}}{{O}_{4}}\left( g \right)2N{{O}_{2}}\left( g \right)\]
    \[\begin{align}   & \operatorname{initial}\,moles\,10 \\  & moles\,at\,eqm.(1-\alpha )2\alpha  \\ \end{align}\]
    Where, \[\alpha \]=degree of dissociation
    Total number of moles at equilibrium.
    \[=(1-\alpha )+2\alpha =(1+\alpha )\]
    \[{{P}_{{{N}_{2}}{{O}_{4}}}}=\frac{(1-\alpha )}{(1+\alpha )}\times P\,\,;\,\,{{P}_{N{{O}_{2}}}}=\frac{2a}{(1+\alpha )}\times P\]
    \[{{K}_{P}}=\frac{{{({{p}_{N{{O}_{2}}}})}^{2}}}{{{p}_{{{N}_{2}}{{O}_{4}}}}}=\frac{{{\left( \frac{2a}{1+a}\times p \right)}^{2}}}{\left( \frac{1-\alpha }{1+\alpha } \right)\times P}=\frac{4{{\alpha }^{2}}P}{{{(1-\alpha )}^{2}}}\]
    Given, \[{{K}_{p}}=2\],            \[P=0.5atm\]
    \[\therefore \]      \[{{K}_{p}}=\frac{4{{\alpha }^{2}}P}{1-{{\alpha }^{2}}};2=\frac{4{{\alpha }^{2}}\times 0.5}{1-{{\alpha }^{2}}}\]
    \[\alpha =0.707\approx 0.71\]
    \[\therefore \]Percentage dissociation
    \[=0.71\times 100=71\]


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