2023 AMC 10A Problems/Problem 25

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25. Let HA represent a weak monoprotic acid with Ka = 1.0×10−5. In an experiment, a 50.0 mL sample of 0.10 mol L−1 HA(aq) is titrated with 0.10 mol L−1 NaOH(aq). At which point during the titration are the equilibrium concentrations of H+ and OH− equal? A after the addition of exactly 25.0 mL of NaOH(aq)

B after the addition of slightly less than 50.0 mL of NaOH(aq)

C after the addition of exactly 50.0 mL of NaOH(aq)

D after the addition of more than 50.0 mL of NaOH(aq)

E The equilibrium concentrations of H+ and OH− are never equal. -Kaisssssgao