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JEE Main & Advanced Chemistry Equilibrium / साम्यावस्था Question Bank Hydrogenion concentration pH scale and buffer solution

  • question_answer
    How much sodium acetate should be added to a \[0.1\,\,m\] solution of \[C{{H}_{3}}COOH\] to give a solution of \[pH=5.5\,(p{{K}_{a}}\] of \[C{{H}_{3}}COOH=4.5)\]        [KCET 1996]

    A)                 \[0.1\,\,m\]       

    B)                 \[0.2\,\,m\]

    C)                 \[1.0\,\,m\]       

    D)                 \[10.0\,\,m\]

    Correct Answer: C

    Solution :

               \[pH=p{{K}_{a}}+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}\]; \[5.5=4.5+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ 0}\text{.1 }\!\!]\!\!\text{ }}\]                    \[\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{0.1}=5.5-4.5=1\]                                 \[\frac{\text{ }\!\![\!\!\text{ Salt}]}{0.1}=\]antilog 1 = 10 ;  \[\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }=1\]


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