Equilibrium Question 401
Question: pH of a solution of $ 10,ml $ . 1N sodium acetate and $ 50,ml $ 2N acetic acid $ (K_{a}=1.8\times {10^{-5}}), $ is approximately [MP PMT 2003]
Options:
A) 4
B) 5
C) 6
D) 7
Show Answer
Answer:
Correct Answer: A
Solution:
$ pH=pK_{a}+log\frac{[\text{ Salt }]}{[\text{ Acid }]} $
$ pH=-\log ,(1.8\times {10^{-5}})+\log \frac{[10]}{[100]} $
$ =-\log 1.8+5+\log {10^{-1}} $
$ =-\ 0.2553+5-1=3.7447,or=4 $
