J & K CET Engineering J and K - CET Engineering Solved Paper-2012

  • question_answer
    pH of 0.0002 M formic acid\[[{{K}_{a}}=2\times {{10}^{-4}}]\] approximately is

    A)  1.35            

    B)  0.5

    C)  3.7             

    D)  1.85               

    Correct Answer: C

    Solution :

     \[{{[{{H}^{+}}]}_{HCOOH}}=\sqrt{{{K}_{a}}.C}\] \[=\sqrt{2\times {{10}^{-4}}\times 0.0002}\] \[pH=-\log [{{H}^{+}}]=-\log (2\times {{10}^{-4}})\] \[=3.69\approx 3.7\]


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