We’re being asked to determine the acid dissociation constant (Ka) for a weak monoprotic acid.
Recall that at the equivalence point of a titration:
Also, recall that moles = molarity × volume.
The weak acid is monoprotic so it ha only one H+ to donate and one equivalence point:
HA → H+ + A- Ka Equivalence Point
(MA)acid = (MV)base
A 0.70 g sample of a weak monoprotic acid was dissolved in 150 mL of water and titrated with a 0.055 M solution of KOH at 25°C. At the half-equivalence point, after addition of 25.5 mL of the KOH solution, the pH was 3.8.
Determine the acid dissociation constant for this weak acid at 25°C.
Frequently Asked Questions
What scientific concept do you need to know in order to solve this problem?
Our tutors have indicated that to solve this problem you will need to apply the Equivalence Point concept. If you need more Equivalence Point practice, you can also practice Equivalence Point practice problems.