Equilibrium Question 285
Question: $ pK_{a} $ of acetic acid is $ 4.74 $ . The concentration of $ CH_3COONa $ is 0.01 M. The pH of $ CH_3OONa $ is [Orissa JEE 2004]
Options:
A) 3.37
B) 4.37
C) 4.74
D) 0.474
Show Answer
Answer:
Correct Answer: A
Solution:
$ {H^{+}}=c,.,\alpha =\sqrt{K_{a},.,c} $
$ pH=-\log {{( \sqrt{K_{a}.,c} )}^{1/2}} $
$ =\frac{1}{2}[-\log K_{a}-\log c] $
$ =\frac{1}{2}[4.74-\log {10^{-2}}] $
$ =\frac{1}{2}[4.74+2]=3.37 $ .
