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The pH of the solution containing \mathrm{50 \mathrm{~mL}} each of \mathrm{ 0.10 \mathrm{M}} sodium acetate and \mathrm{ 0.01 \mathrm{M}} acetic acid is [Given \mathrm{pK}_{a} \mathrm{of} \: \mathrm{CH}_{3} \mathrm{COOH}={4.57} ]
 

Option: 1

3.57


Option: 2

4.57


Option: 3

2.57


Option: 4

5.57


Answers (1)

best_answer

Given salt ( sodium acetate ), \mathrm{M=0.10,V=50mL}  Weak acid

\mathrm{\left ( CH_{3}COOH \right ),pKa=4.57} and  \mathrm{M=0.01} So, weak acid and salt form an

acidic buffer

Then, \mathrm{p{H} =p K_{a}+\log \frac{[\text { salt] }]}{[\text { Acid] }}} \\

         \mathrm{p{H} =4.57+\log \frac{(0.1)}{(0.01)}} \\

         \mathrm{p{H} =5.57 }

Trick: acetate ion is a base and if we add base in acid the \mathrm{p{H} } of solution will

increase. So, \mathrm{p{H} } of solution will be greater than 4.57

Hence the correct option is 4.

Posted by

vinayak

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