You dissolve 1.00 gram of an unknown diprotic (two titratable protons) acid in 200.0 mL of H2O. This solution is just neutralized by 5.00 mL of a 1.00 M NaOH solution. What is the molar mass of the unknown acid?
A. 25
B. 50
C. 200
D. 400
E. none of these