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JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
                    What would be the pH of a solution obtained by mixing 5g of acetic acid and 7.5g of sodium acetate and making the volume equal to 500 mL?                 \[(\operatorname{Ka}=1.75\times {{10}^{-5}},\operatorname{pka}=4.6)\]     JEE Main Online Paper ( Held On 25  April 2013 )

    A)                 pH =4.70

    B)                                        pH< 4.70

    C)                                        pH of solution will be equal to pH of acetic acid

    D)                                        4.76 < pH< 5.0

    Correct Answer: D

    Solution :

                    \[pH=p{{K}_{a}}+\log \frac{\text{ }\!\![\!\!\text{ salt }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ acid }\!\!]\!\!\text{ }}\] \[=4.76+\log \frac{\frac{7.5}{500}}{\frac{5}{500}}=4.7+\log 1.5=4.87\] Hence correct answer is 4.76 < pH < 5.0


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