Calculate the pH of a buffer solution prepared by mixing 20 mL of 5.0% acetic acid...

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Chemistry

Calculate the pH of a buffer solution prepared by mixing 20 mLof 5.0% acetic acid with 20 mL of 0.50 M NaOH and 100 mL ofwater

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3.7 Ratings (321 Votes)

5% acetic acid molarity = 0.833 M

millimoles of acetic acid = 0.833 x 20 = 16.66

NaOH millimoles = 0.50 x 20 = 10

CH3COOHÂ Â +Â Â NaOH -----------------------------> CH3COONa + H2O

16.66Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 10Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0Â Â Â Â Â --------------> initial

6.66Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 10Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 10 ----------------> after reaction

pKa of acetic acid = 4.74

pH = pKa + log [CH3COONa]/[CH3COOH]

pH = 4.74 + log (10 / 6.66)

pH = 4.92

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