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20/10/2021 9:58 am
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A buffer solution is prepared by mixing 10 mL of 1.0 M CH3COOH and 20 mL of 0.5 M CH3COONa and then diluted to 100 mL with distilled water. If pKa of CH3COOH is 4.76, what is the pH of the buffer solution?
(a) 5.8
(b) 4.34
(c) 5.21
(d) 4.76
1 Answer
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20/10/2021 10:02 am
Correct answer: (d) 4.76
Explanation:
Total volume = 100 mL
[acid] = 10 mL x \(\frac{1.0}{100}\) = 0.1
[salt] = 20 mL x \(\frac{0.5}{100}\) = 0.1
pH of acidic buffer = pKa + log \(\frac{[salt]}{[acid]}\)
= 4.76 + log \(\frac{0.1}{0.1}\) = 4.76