J.R. S. answered 05/01/22
Ph.D. University Professor with 10+ years Tutoring Experience
If it took 12 ml of base, then you can find the moles of base, and hence the moles of acid in the 25.0 ml.
Moles base:
12 mls NaOH x 1 L / 1000 mls x 0.50 mols/L = 0.006 mols NaOH
Moles acid:
0.006 mols NaOH x 1 mol CH3COOH / mol NaOH = 0.006 mols CH3COOH
Concentration of CH3COOH:
moles / Liters
0.006 mols / 25.00 ml x 1000 ml / L = 0.24 moles / L = 0.24 M
The pH will be greater than 7 since you are titrating a weak acid with a strong base.