NEET Chemistry Equilibrium / साम्यावस्था NEET PYQ-Chemical Equilibrium

  • question_answer
    For a given exothermic reaction, \[{{K}_{p}}\] and \[K_{p}^{'}\] are the equilibrium constants at temperatures  \[{{T}_{1}}\] and\[{{T}_{2}},\] respectively. Assuming that heat of reaction is constant in 'temperature range between \[{{T}_{1}}\] and\[{{T}_{2}},\] it is readily observed that                                                          [AIPMT 2014]

    A)

    B)  \[{{K}_{p}}<K_{p}^{'}\]       

    C)  \[{{K}_{p}}=K_{p}^{'}\]       

    D)       \[{{K}_{p}}=\frac{1}{K_{p}^{'}}\]

    Correct Answer: A

    Solution :

     \[{{K}_{p}}>K_{p}^{'}\]     
    The equilibrium constant at two different temperatures for a thermodynamic process is given by
    \[\log \frac{{{k}_{2}}}{{{k}_{1}}}=\frac{\Delta {{H}^{{}^\circ }}}{2.303R}\left[ \frac{1}{{{T}_{1}}}-\frac{1}{{{T}_{2}}} \right]\]
    Here, \[{{K}_{1}}\] and \[{{K}_{2}}\] are replaced by \[{{K}_{p}}\] and\[K{{'}_{p}}.\]
    Therefore, \[\log \frac{K{{'}_{p}}}{{{K}_{p}}}=\frac{\Delta H{}^\circ }{2.303R}\left[ \frac{1}{{{T}_{1}}}-\frac{1}{{{T}_{2}}} \right]\]
    For exothermic reaction, \[{{T}_{2}}>{{T}_{1}}\] and  \[\Delta H=-ve\]
    \[\therefore \]                       \[{{K}_{p}}>K{{'}_{p}}\]


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