he following K a values have been experimentally determined for formic and aceti
ID: 635969 • Letter: H
Question
he following Ka values have been experimentally determined for formic and acetic acids.
Which of the following solutions will have the highest pH?
b.
What is the pH of a buffer solution of 0.10 M solution of acetic acid and 0.10 M sodium acetate? Support your answer.
4.74
C.if 0.05 mol of sodium hydroxide, NaOH, are added to the acetic acid/acetate buffer from part B, what would be the resulting pH? (Recall: the original buffer had 0.10 M acetic acid and 0.10 M acetate.). Show/describe your work.
Acid Ka Formic acid, HCO2H 1.8x10-4 Acetic acid, CH3CO2H 1.8x10-5Explanation / Answer
a) answer: 1.0 M sodium acetate, NaCH3CO2
pka of CH3COOH = -logKa
= -log(1.8*10^-5)
= 4.74
pH of CH3COONa = 7+1/2(pka + logC)
= 7+1/2(4.74+log1)
= 9.37
but not others,
b) pH of acidic buffer = pka + log(CH3COONa/CH3COOH)
pH = 4.74+log(0.1/0.1) = 4.74
answer: 4.74
c) no of mol of NaOH = 0.05 mol
pH of acidic buffer = pka + log(CH3COONa+NaOH/CH3COOH-NaoH)
pH = 4.74+log((0.1+0.05)/(0.1-0.05))
pH = 5.22
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