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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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ripterscoot ripterscoot
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11 years ago
What ratio of ethanoic acid to sodium ethanoate concentration is required to give a buffer solution of pH 5.70?  Use Ka(CH3COOH) = 1.8 x 10^?5
I got the answer 9.02 but the answer given was 0.11, because my teacher for some reason used 10^-0.96 instead of 10^0.96
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#1
11 years ago
pH = pKa + log[A-/HA]

Ka = 1.8E-5, pKa = -log[Ka] = 4.74

5.70 = 4.74 + log[CH3COONa]/[CH3COOH]

0.955 = log[CH3COONa]/[CH3COOH]

9.02 = [CH3COONa]/[CH3COOH]

You need 9x more sodium acetate than acetic acid.
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