A) 3.84
B) 4.76
C) 4.34
D) 5.21
Correct Answer: B
Solution :
Buffer solution is prepared by mixing 10 mL of \[\text{1}\,\text{MC}{{\text{H}}_{\text{3}}}\text{COOH}\]and 20 mL of \[\text{0}\text{.5}\,\text{MC}{{\text{H}}_{\text{3}}}\text{COONa}\] Volume of solution =100 mL Now, the concentration of \[\text{C}{{\text{H}}_{\text{3}}}\text{COOH}\] Before dilution =After dilution \[{{M}_{1}}{{V}_{1}}={{M}_{2}}{{V}_{2}}\] \[1\times 10=\,{{M}_{2}}\times 100\] \[{{M}_{2}}=\frac{10}{100}=\frac{1}{10}\] Similarly, the concentration of \[C{{H}_{3}}COONa\] Before dilution = After dilution \[{{M}_{1}}{{V}_{1}}={{M}_{2}}{{V}_{2}}\] \[0.5\times 20={{M}_{2}}\times 100\] \[{{M}_{2}}=\frac{0.5\times 20}{100}=\frac{1}{100}M\] Then, \[pH=p{{K}_{aa}}+\log \frac{[Salt]}{[Acid]}\] \[=4.76+\log \frac{0.1}{0.1}\] \[pH=4.76\]
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