BHU PMT BHU PMT Solved Paper-2001

  • question_answer
    \[2HCl(g){{H}_{2}}(g)+C{{l}_{2}}(g)\] For the above reaction, the equilibrium constant is\[1.2\times {{10}^{-4}}M,\]. If the equilibrium concentration of\[{{H}_{2}}\]and\[C{{l}_{2}}\]is\[1.2\times {{10}^{-3}}M\]and \[1.2\times {{10}^{-4}}M\] respectively, then the concentration of\[HCl\]is:

    A) \[12\times {{10}^{-4}}M\]

    B) \[12\times {{10}^{-3}}M\]

    C)  \[12\times {{10}^{-2}}M\]          

    D) \[12\times {{10}^{-1}}M\]

    Correct Answer: C

    Solution :

                      We will use expression\[K=\frac{[{{H}_{2}}][C{{l}_{2}}]}{{{[HCl]}^{2}}}\] Given,\[K=1.0\times {{10}^{-5}}[{{H}_{2}}]=1.2\times {{10}^{-3}}M\]                 \[K=\frac{[{{H}_{2}}][C{{l}_{2}}]}{{{[HCl]}^{2}}}\] or            \[{{[HCl]}^{2}}=\frac{[{{H}_{2}}][C{{l}_{2}}]}{K}\] or            \[[HCl]=\sqrt{\frac{[{{H}_{2}}][C{{l}_{2}}]}{K}}\] Substituting the values \[=\sqrt{\frac{1.2\times {{10}^{-3}}\times 1.2\times {{10}^{-4}}}{1.0\times {{10}^{-5}}}}\] \[=\sqrt{1.2\times 1.2\times {{10}^{-7}}\times {{10}^{5}}}\] \[=\sqrt{\frac{1.2\times 1.2}{100}}\] \[=0.12\text{ }M=12\times {{10}^{-2}}M\]


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