Equilibrium Question 833
Question: A buffer solution is prepared by mixing 10 mL of $ 1.0M,CH_3COOH $ and 20 mL of 0.5 M $ CH_3COONa $ and then diluted to 100 mL with distilled water. If $ pK_{a} $ of $ CH_3COOH $ is 4.76, what is the pH of the buffer solution'
Options:
A) 5.8
B) 4.34
C) 5.21
D) 4.76
Show Answer
Answer:
Correct Answer: D
Solution:
Total volume $ =100mL $
$ [ acid ]=10mL\times \frac{1.0}{100}=0.1 $
$ [ salt ]=20mL\times \frac{0.5}{100}=0.1 $ pH of acidic buffer $ =pK_{a}+\log \frac{[salt]}{[acid]} $
$ =4.76+log\frac{0.1}{0.1}=4.76 $
