Answer:
b. 0.100M
Explanation:
The balanced chemical reaction is: NaOH + HA ⇒ H₂O + NaA
The NaOH and HA react in a 1:1 molar ratio, so at the equivalence point, the amount of NaOH added equals the amount of HA that was present in the solution.
The amount of NaOH that was added can be calculated and set equal to the amount of HA that must have been present to react with it.
n = CV = (0.200 mol/L)(12.5 mL) = 2.50 mmol NaOH = 2.50 mmol HA
Thus, there were 2.50 mmol of HA in 25.0 mL. The concentration can be calculated as follow:
C = n/V = (2.50 mmol)/(25.0mL) = 0.100 M
