A 0.625 g sample of an unknown weak acid (call it HA for short) is dissolved in enough water to make 25.0 mL of solution. This weak acid solution is then titrated with 0.100 M NaOH, and 45.0mL of the NaOH solution is required to reach the equivalence point. Using a pH meter, the pH of the solution at the equivalence point is found to be 8.25. (a) Determine the molecular mass of the unknown acid. (b) Determine the pKa value of the unknown acid.