Directions:

"Refer back to equation (2), and consider carefully whether you could simply have used the pH value of the solution at the very beginning of the titration, before any base had been added, to determine either or both the molar mass and the Ka value.  Which of the following is the best conclusion:"

The second equation was:

Ka = (H3O+) (A-) / (HA)

A.  The initial solution  pH depend on both the Ka and the concentration of the weak acid, so measuring the initial pH is insufficient to determine both these solutions.

B.  The initial solution  pH depend on both the Ka and the concentration of the weak acid, so measuring the initial pH very accurately may be sufficient to determine both these unknowns.