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 $ .
