0.10 mol of NaOH is added to 0.30 mol of weak acid HX in a total volume of 1.00 L. The pH of the resultant solution is 8.65. What is Ka for HX

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?