Equilibrium Question 429

Question: The $ pH $ of a simple sodium acetate buffer is given by $ pH=pK_{a}+\log \frac{[Salt]}{[Acid]} $

$ K_{a} $ of acetic acid $ =1.8\times {10^{-5}} $ If [Salt] = [Acid] = 0.1 M, the $ pH $ of the solution would be about [BHU 1987]

Options:

A) 7

B) 4.7

C) 5.3

D) 1.4

Show Answer

Answer:

Correct Answer: B

Solution:

[Salt]= 0.1 M, [Acid]= 0.1 M $ K_{a}=1.8\times {10^{-5}} $ ; $ pH=-\log K_{a}+log\frac{[\text{ Salt }]}{[\text{ Acid }]} $

$ =-log1.8\times {10^{-5}}+log\frac{0.1}{0.1} $

$ =-log1.8\times {10^{-5}} $

$ pH=4.7 $ .



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