JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    What will be the degree of ionisation of \[0.05\,\,M\] acetic acid if its \[p{{K}_{a}}\] value is\[4.74\]?

    A) \[0.019%\]

    B)  \[1.9%\]

    C)  \[3.0%\]                             

    D) \[4.74%\]

    Correct Answer: B

    Solution :

                    \[C{{H}_{3}}COOHC{{H}_{3}}CO{{O}^{-}}+{{H}^{+}}\] Initial          1                          0                     0 At equili     \[1-\alpha \]      \[\alpha \]                   \[\alpha \]                 \[p{{K}_{a}}=-\log {{K}_{a}}=4.74\] \[\therefore \]  \[{{K}_{a}}=\text{antilog}(4.74)1.82\times {{10}^{-5}}\] From     \[{{K}_{a}}=\frac{C{{\alpha }^{2}}}{(1-\alpha )}=C{{\alpha }^{2}}\]             \[(1-\alpha \approx 1)\] \[\alpha =\sqrt{\frac{{{K}_{a}}}{C}}=\sqrt{\frac{1.82\times {{10}^{-5}}}{0.05}}=0.019\]or\[1.9%\]


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