1. Acids
Lesson 16
Amphiprotic
Ions
Acids or Bases?

2. Amphiprotic Ions
H3PO4 Acid
H2PO4- Amphiprotic
HPO42- Amphiprotic
PO43- Base
Amphiprotic ions have a Ka and a Kb. If you compare them, you can tell how the ion will behave in water as either an acid or base.
If the Ka > Kb, then the ion is an acid.
If the Kb > Ka, then the ion is an base.

3. 1. Is H2PO4- an acid or base when in water. Write the
1. Is H2PO4- an acid or base when in water? Write the hydrolysis equation for this ion.
Ka (H2PO4-) = 6.2 x 10-8
Kb (H2PO4-) = = Kw
Ka(H3PO4)
= 1 x
7.5 x 10-3
= 1.3 x
Ka > Kb Acid
H2PO H2O ⇄ HPO42- + H3O+

4. 2. Is HPO42- an acid or base when in water. Write. the
2. Is HPO42- an acid or base when in water? Write the hydrolysis equation for this ion.
Ka (HPO42-) = 2.2 x
Kb (HPO42-) = = Kw
Ka(H2PO4-)
= 1 x
6.2 x 10-8
= 1.6 x 10-7
Kb > Ka base
HPO H2O ⇄ H2PO4- + OH-

5. 3. Show by calculation if NH4F is an acid or base when in water.
NH4F → NH F-
acid base
Both have weak parents- neither will cross off!
What will the salt be?
Ka(NH4+) = 5.6 x
Kb (F-) = = Kw
Ka(HF)
= 1 x
3.5 x 10-4
= 2.9 x
Ka > Kb acid

6. 4. Show by calculation if NH4CH3COO is an acid or base when in water.
NH4CH3COO → NH CH3COO-
acid base
Ka(NH4+) = 5.6 x
Kb (CH3COO-) = = Kw
Ka(CH3COOH)
= 1 x
1.8 x 10-5
= 5.6 x
Ka = Kb neutral pH = 7.00

7. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M

8. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M
L KOH

9. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M
L KOH x mol L

10. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M
L KOH x mol x 1 mole H2CO3
L mole KOH

11. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M
L KOH x mol x 1 mole H2CO3 x L
L mole KOH mol

12. 5. Calculate the volume of 0. 100 M H2CO3 required to. neutralize 25
5. Calculate the volume of M H2CO3 required to neutralize 25.0 mL of M KOH.
1H2CO KOH → K2CO HOH
? L L
0.100 M M
L KOH x mol x 1 mole H2CO3 x L = L
L mole KOH mol

13. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Mg(OH)2(s) ⇌ Mg2+ + 2OH-
CN- + H2O ⇌ HCN + OH-
NH4+ + H2O ⇌ H3O+ + NH3
  N2O4(g) ⇌ 2NO2(g)
2H2O ⇌ H3O+ + OH-

14. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Ksp Mg(OH)2(s) ⇌ Mg2+ + 2OH-
CN- + H2O ⇌ HCN + OH-
NH4+ + H2O ⇌ H3O+ + NH3
  N2O4(g) ⇌ 2NO2(g)
2H2O ⇌ H3O+ + OH-

15. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Ksp Mg(OH)2(s) ⇌ Mg2+ + 2OH-
Kb CN- + H2O ⇌ HCN + OH-
NH4+ + H2O ⇌ H3O+ + NH3
  N2O4(g) ⇌ 2NO2(g)
2H2O ⇌ H3O+ + OH-

16. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Ksp Mg(OH)2(s) ⇌ Mg2+ + 2OH-
Kb CN- + H2O ⇌ HCN + OH-
Ka NH4+ + H2O ⇌ H3O+ + NH3
  N2O4(g) ⇌ 2NO2(g)
2H2O ⇌ H3O+ + OH-

17. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Ksp Mg(OH)2(s) ⇌ Mg2+ + 2OH-
Kb CN- + H2O ⇌ HCN + OH-
Ka NH4+ + H2O ⇌ H3O+ + NH3
  Keq N2O4(g) ⇌ 2NO2(g)
2H2O ⇌ H3O+ + OH-

18. 6. Label the equation that has a Ka, Kb, Ksp, Kw, or Keq.
Ksp Mg(OH)2(s) ⇌ Mg2+ + 2OH-
Kb CN- + H2O ⇌ HCN + OH-
Ka NH4+ + H2O ⇌ H3O+ + NH3
  Keq N2O4(g) ⇌ 2NO2(g)
Kw 2H2O ⇌ H3O+ + OH-