Equilibrium Question 428
Question: A buffer solution has equal volumes of $ 0.2M,NH_4OH $ and $ 0.02M,NH_4Cl $ . The $ pK_{b} $ of the base is 5. The pH is [CBSE PMT 1989; KCET 2005]
Options:
A) 10
B) 9
C) 4
D) 7
Show Answer
Answer:
Correct Answer: A
Solution:
$ pOH=pK_{b}+\log \frac{[salt]}{[\text{ base }]} $
$ =5+\log \frac{0.02}{0.2}=5+\log \frac{1}{10}=5+(-1)=4 $
$ pH=14-pOH=14-4=10 $
