1. Acidic and Basic Salts A salt is an ionic compound that contains a
cation other than H+ and an anion other than
OH-.
CaSO4, BaI2
When a salt undergoes hydrolysis, the
resulting aqueous solution may be acidic,
basic, or remain neutral.
To determine the acidity of the resulting
solution, you must look at the resulting
cations and anions.

2. Acidic and Neutral Cations
Cations can be either acidic or neutral but not
basic.
Cations producing an acidic solution are
NH4+, and the transition metal ions which can
form complex ions (Zn, Cu, Al, Ni).
NH4+(aq) H+(aq) + NH3(aq)
Al3+(aq) + 6H2O(l) Al(H2O)63+(aq)
Al(H2O)63+(aq) H+(aq) Al(H2O)5(OH)2+(aq)

3. Note the following cations which are
spectators.
Li+, Na+, K+, Ca2+, Ba2+, Sr2+
These cations are found in strong bases.
If a strong base wants to completely
dissociate, why would its cation want to
undergo hydrolysis to reform the base?
These cations will not undergo hydrolysis.
There are no basic cations.

4. Basic and Neutral Anions
Anions can be either basic or neutral but not
acidic.
Anions producing a basic solution are
C2H3O2-, F-, CO32-, PO43-, CN-, NO2-, and S2-.
C2H3O2- (aq) + H2O(l) HC2H3O2 (aq) +
OH-(aq)

5. Note the following anions which are
spectators.
Cl-, Br-, I-, NO3-, ClO4-, SO42-
These species are conjugate bases of strong
acids.
Remember, the stronger the acid, the weaker
its conjugate base.
If a molecule wants to completely ionize, why
would its anion want to undergo hydrolysis?

6. Acidic, Basic, or Neutral Salt?
LiClO4 - acidic, basic, or neutral?
Is the cation, Li+, a metallic ion of Group I
or Group II?
Yes, as it is found in a strong base
(LiOH), and will be a spectator.

7. Is the anion, ClO4-, the conjugate base of
a strong acid, HClO4?
Yes, therefore it will be a spectator.
Both cation and anion are spectators,
therefore LiClO4 is a neutral salt.

8. Cu(NO3)2 - acidic, basic, or neutral?
Is the cation, Cu2+, a metallic ion of
Group I or Group II?
No but Cu2+ being a transition metal will
hydrolyze producing an acidic solution.
Cu2+ with vacant orbitals will act as a
Lewis acid and will be an electron
acceptor.

9. Cu2+(aq) + 4H2O(l) Cu(H2O)42+(aq)
Cu(H2O)42+(aq) will in turn act as an
Arrhenius or Bronsted-Lowry acid.
Cu(H2O)42+(aq) H+(aq) +
Cu(H2O)3(OH)+(aq)
Is the anion, NO3-, the conjugate base of
a strong acid, HNO3?
Yes, therefore it will be a spectator.

10. The salt will be acidic due to the Cu2+.

11. NaH2PO4 - acidic, basic, or neutral?
Is the cation, Na+, a metallic ion of
Group I or Group II?
Yes, as it is found in a strong base
(NaOH), and will be a spectator.

12. Is the anion, H2PO4-, the conjugate base
of a strong acid, H3PO4?
No because H3PO4 is a weak acid.
Before saying that NaH2PO4 is a neutral
salt, you must ask is H2PO4-
amphiprotic?
If the anion, H2PO4-, is not amphiprotic,
then the solution will be basic!

13. If the anion, H2PO4-, is amphiprotic then
you must determine if the salt is acidic
or basic!
H2PO4- is amphiprotic, therefore you
must compare the Ka of H2PO4- to the Kb
of H2PO4-.
If H2PO4- (dihydrogen phosphate) acts as
an acid the following is true.
H2PO4-(aq) H+(aq) + HPO42-(aq)
Ka(H2PO4-) = 6.2 × 10-8

14. If H2PO4- acts as a base the following is
true.
H2PO4-(aq) + H2O(l) H3PO4(aq) +
OH-(aq)
The Kb for H2PO4- is not given in a table
of Dissociation Constants for Acids and
Bases at 25°C.

15. However, it can be calculated from the
relationship between an acid and its
conjugate base given by,
Ka × Kb = Kw
and its hydrolysis equation.
H2PO4-(aq) + H2O(l) H3PO4(aq) + OH-(aq)
Ka(H3PO4) = 7.5 × 10-3, therefore

16. Kw Ka
10-14 Kb = = =
1.3 × 10-12
7.5 × 10-3
Ka > Kb, therefore NaH2PO4 is an acidic salt.

17. Acidic, Basic, Neutral Salt WrapUp
Is the cation a metallic ion from Group I or II?
If yes, the cation will be a spectator ion.
If no, it will most likely be acidic because
the cation will be a transition metal.
Is the anion the conjugate base of a strong
acid?
If yes, the anion will be a spectator ion.

18. If the anion is not a spectator ion, is it
amphiprotic?
If yes, then it can be either acidic or
basic.
If Ka > Kb, then the species is acidic.
If Kb > Ka, then the species is basic.
If no, then the salt will be basic.