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

  • question_answer
    For preparing a buffer solution of \[pH\]6 by mixing sodium acetate and acetic acid, the ratio of the concentration of salt and acid should be\[({{K}_{a}}={{10}^{-5}})\]      [MP PET 1997]

    A)                 \[1\,\,:\,\,10\]  

    B)                 \[10\,\,:\,\,1\]

    C)                 \[100\,\,:\,\,1\]

    D)                 \[1\,\,:\,\,100\]

    Correct Answer: B

    Solution :

               \[{{K}_{a}}={{10}^{-5}}\] ; \[pH=6\]                    \[pH=-\log {{K}_{a}}+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}\] ;                              \[6=-\text{log}{{10}^{-5}}+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}\]                    \[6=5\text{log}10+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}\]; \[6=5+\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}\]                                 \[\text{log}\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}=6-5=1\]; \[\frac{\text{ }\!\![\!\!\text{ Salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ Acid }\!\!]\!\!\text{ }}=\frac{10}{1}\]


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