JEE Main & Advanced Chemistry Equilibrium / साम्यावस्था Sample Paper Topic Test - Chemical Equilibrium

  • question_answer
    The equilibrium constants at 1140 K for these two reactions are
    \[2CO(g)C(s)+C{{O}_{2}}(g);{{K}_{p1}}={{10}^{-12}}at{{m}^{-1}}\]
    \[CO(g)+C{{l}_{2}}(g)COC{{l}_{2}}(g);{{K}_{p2}}=3\times {{10}^{-3}}\text{at}{{\text{m}}^{-1}}\]
    What will be equilibrium constant \[{{K}_{c}}\] for the following reaction at 1140 K?
    \[C(s)+C{{O}_{2}}(g)+2C{{l}_{2}}(g)2COC{{l}_{2}}(g)\]

    A) \[8.42\times {{10}^{8}}{{M}^{-1}}\]

    B) \[8.42\times {{10}^{4}}{{M}^{-1}}\]

    C) \[4.21\times {{10}^{4}}{{M}^{-1}}\]

    D) \[4.21\times {{10}^{8}}{{M}^{-1}}\]

    Correct Answer: A

    Solution :

    [a] \[C(s)+C{{O}_{2}}(g)2CO(g)\]           ?(i)
    \[K{{'}_{{{p}_{1}}}}={{10}^{12}}atm,K{{'}_{{{p}_{1}}}}\frac{1}{{{K}_{{{p}_{1}}}}}=\frac{1}{{{10}^{-12}}}\]
    \[2CO(g)+2C{{l}_{2}}(g)2COC{{l}_{2}}(g)\]      ?(ii)
    \[{{K}_{p{{'}_{2}}}}={{(3\times {{10}^{-3}})}^{2}}\text{at}{{\text{m}}^{\text{-2}}}{{K}_{p{{'}_{2}}}}={{({{K}_{{{p}_{2}}}})}^{2}}\]
    Adding Egs. (i) and (ii), we get
    \[C(s)+C{{O}_{2}}(g)+2C{{l}_{2}}(g)2COC{{l}_{2}}(g)\]
    \[{{K}_{p}}={{10}^{12}}\times 9\times {{10}^{-6}}=9\times {{10}^{6}}\]
    \[\Delta ng=2-(1+2)=-1,{{K}_{p}}={{K}_{c}}{{(RT)}^{-1}}\]
    \[{{K}_{c}}={{K}_{p}}(RT)\]
    \[{{K}_{c}}=9\times {{10}^{6}}\times 0.0821\times 1140\]
    \[=8.42\times {{10}^{8}}{{M}^{-1}}\]


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