Hey, I answered that question for you yesterday, but my answer was cut off since I was late by 1 second, literally...

1. Concentration of acetic acid in the final 35 mL (25 mL + 10 mL):

New acid concentration:

(25.00 mL × 0.110 M) / (35.0 mL) = 0.0786 M

New base concentration:

(10 mL x 0.138 M) / 35.0 mL = 0.0394 M

pH = pKa + log10 [conjugate base] / [acid]

pKa = 4.75

pH = 4.75 + log (0.0394/0.0786)= 4.75 + log (0.5) = 4.75 – 0.3 = 4.45

2. Concentration of acetic acid in the final 45 mL:

(25.00 mL × 0.110 M) / (45.0 mL) = 0.061 M

(20 mL x 0.138 M) / 45.0 mL = 0.061 M

log (1) = 0

pKa = 4.75 = pH

pH = 4.75

(25.00 mL × 0.110 M) / (55.0 mL) = 0.05 M

(30 mL x 0.138 M) / 55.0 mL = 0.0753 M

pH = pKa + log10 [conjugate base] / [acid] = 4.75 + log (0.0753/0.05) = 4.75 + 0.1778 = 4.93

pH = 4.93

It says that the answer is all incorrect :( This is a new question from yesterday! thank you so much for your help i really appreciate. Would you mind checking this problem again?

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