What is the pH of the solution created by combining 12.00 mL of the 0.10 M NaOH with 8.00 mL of the 0.10 M HC2H3O2?
Write the equation and balance it.
Then determine the moles of NaOH and moles acetic acid. M x L = moles.
Next you must look at the moles and determine which is in excess, if either, and recognize the kind of solution produced. If an excess of NaOH, the pH will be determined by the OH from NaOH. If acetic acid, there will be some acetic acid and some acetate ion; the result will be a buffered solution and the Henderson-Hasselbalch equation should be used. Post yur work if you get stuck.