CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    1.6 moles of\[PC{{l}_{5}}(g)\]is placed in\[4\text{ }d{{m}^{3}}\]closed vessel. When the temperature is raised to 500 K, it decomposes and at equilibrium 1.2 moles of\[PC{{l}_{5}}(g)\]remains. What is the\[{{K}_{c}}\]value for the decomposition of\[PC{{l}_{5}}(g)\]to\[PC{{l}_{3}}(g)\]and\[C{{l}_{2}}(g)\]at 500 K?

    A) 0.013                                    

    B) 0.050

    C) 0.033                    

    D)        0.067

    E)  0.045

    Correct Answer: C

    Solution :

    \[PC{{l}_{5}}PC{{l}_{3}}+C{{l}_{2}}\] \[\begin{matrix}    1.6 & 0 & \,\,\,\,\,\,\,\,\,0 & Initially  \\    (1.6-x) & x & \,\,\,\,\,\,\,\,\,x & At\,equilibrium  \\    \left( \frac{1.6-x}{4} \right)\,\,\, & \frac{x}{4} & \,\,\,\,\,\,\,\,\,\frac{x}{4} & {}  \\ \end{matrix}\] Given,     \[1.6-x=1.2\]    \[x=0.4\] \[[PC{{l}_{5}}]=\frac{1.2}{4}\] \[[PC{{l}_{3}}]=\frac{0.4}{4}\] \[[C{{l}_{2}}]=\frac{0.4}{4}\] \[{{K}_{c}}=\frac{[PC{{l}_{3}}][C{{l}_{2}}]}{[PC{{l}_{5}}]}\] \[=\frac{\left( \frac{0.4}{4} \right)\left( \frac{0.4}{4} \right)}{\left( \frac{1.2}{4} \right)}\] \[=\frac{0.1\times 0.1}{0.3}\]     \[=0.033\]


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