A buffer solution contains 0.20 M #CH_3COOH# and 0.30 M #CH_3COONa# at #25^oC#? (#Ka=1.8 x10^-5#). What is the pH after the addition of (a) 20.0 mL of 0.050 M #NaOH# or (b) 20.0 mL of 0.050 M #HCl# to 80.0 mL of this buffer solution?

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Answer 1 · 2017-06-04T04:56:31

Buffer pH = 4.93
after adding 20 ml of 0.05M NaOH => pH = 4.96
after adding 20 ml of 0.05M HCl => pH = 4.88

Buffer = 0.20M HOAc + 0.30M NaOAc
Ka(HOAc) = 1.8 x #10^-5# => pKa = -log#Ka# = -log(1.8 x #10^-5#) = 4.75

pH(Bfr) = p#K_a#+ log#[[OAc^-]]/[[HOAc]]# =#4.75 + log((0.30)/(0.20))#= 4.93

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