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CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2000

  • question_answer
    The\[pKa\]of a certain weak acid is 4-0. What should be the [salt] to [acid] ratio if we have to prepare a buffer with pH=5 using the acid and one of the salts?

    A)  10:1                                      

    B)  1:10

    C)  4:5                                        

    D)  5:4

    Correct Answer: A

    Solution :

    \[_{p}{{K}_{a}}\]of weak acid \[=4.0\] We know that\[pH=5,p{{K}_{a}}=4\] \[5=4+1,\log \frac{salt}{acid}=1,\]\[\therefore \]\[\frac{\text{salt}}{\text{acid}}\text{=}\frac{\text{10}}{\text{1}}\]


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