All AP Chemistry Resources
Example Questions
Example Question #93 : Reaction Types
If you have a solution that consist of a weak monoprotic acid (HA), with a pKA of 5.3 and a pH of 3.2, what is the predominant species present?
H3O+
A-
HA
Equal amounts of acid and conjugate base are present.
H2A+
HA
Since pH < pKa the undissociated acid is the predominant form.
Example Question #94 : Reaction Types
If you have a solution that consists of a monoprotic acid (HA), with a pKa of 4.1 and at a pH of 5.8, what is the predominant species present?
Equal amounts of acid and conjugate base are present.
H2A+
HA
H3O+
A-
A-
Since pH > pKA, the deprotonated form of the acid is predominant.
Example Question #95 : Reaction Types
Carbonic acid as a pKa1 = 6.35 and a pKa2=10.33. If the pH is 3.52, what is the predominant species present.
H2CO3
HCO3-
Can not be determined.
H3O+
CO32-
H2CO3
Since pH < pKa1, the undissociated form of carbonic acid (H2CO3) is predominant.
Example Question #96 : Reaction Types
Sulphurous acid (H2SO3) has a pKa1 = 1.92 and a pKa2 = 7.18, if the pH = 5.3, what is the predominant species present?
SO32-
Can not be determined
H2SO3
HSO3-
H3O+
HSO3-
Since pH > pKa1 but pH < pKa2 the predominant form is one with a single hydrogen dissociated.
Example Question #1 : Ph And Pka
Phosphoric acid has a pKa1 = 2.15, a pKa2 = 7.20, and a pKa3 = 12.35. If the pH = 13.0, what is the predominant species present?
HPO42-
H2PO4-
H3PO4
Can not be determined
PO43-
PO43-
Since pH > pKa1, pKa2, and pKa3 the predominant form of the acid is the fully deprotonated form.
Certified Tutor