The document defines different types of acids and bases. Brønsted-Lowry acids are proton donors that donate a proton to a Brønsted-Lowry base, which accepts the proton. Every acid has a conjugate base and every base has a conjugate acid. The conjugate acid has one more hydrogen ion than the conjugate base. Strong acids form weak conjugate bases that do not readily accept protons back, while weak acids form strong conjugate bases that can accept protons. Strong bases form weak conjugate acids that do not readily donate protons, while weak bases form strong conjugate acids that can donate protons. Some substances can act as both acids and bases depending on conditions and are called amphiprotic or amphoteric. Lewis acids are

1. Brønsted-Lowry Acid - substance that donate proton/proton donor
Bronsted-Lowry Base – substance that accept proton/proton acceptor
One species donate proton – one species accept proton
Arrhenius acid - substance dissociate in water produce H+ ion.
Arrhenius base – substance dissociate in water produce OH- ion.
All Arrhenius acid are Bronsted Lowry acid and water must be present
HCI → H+ + CI-
HCI + H2O ↔ H3O+ + CI-
NaOH → Na+ + OH-
NH3 + H2O ↔ NH4
+
+ OH-
CO3
2- + H2O ↔ HCO3
- + OH-
Water/aqueous medium
Water/aqueous medium
Other solvent medium possible
Definition of Acid and Bases
Arrhenius acid Arrhenius baseH+ OH-
2
1
gain H+
Acid + Base ↔ Conjugate Base + Conjugate Acid
lose H+
HCI (acid) - CI- (conjugate base)
lose H+
H2O (base) - H3O+ (conjugate acid)
HCI + H2O ↔ CI- + H3O+
gain H+
Lewis Acid - substance that accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance that donate electron/electron donor, lone pair electron
Lewis Base - donate electron pair forming dative/coordinate bond with Lewis acid
3
HCI + H2O → CI- + H3O+
H2O donate e-
HCI accept e-
Lewis acid Lewis base
Conjugate acid
base pair differ
by one proton

2. Bronsted BaseBronsted Base
Bronsted BaseBronsted Base
Brønsted-Lowry Acid - substance that donate proton/proton donor
Bronsted-Lowry Base – substance that accept proton/proton acceptor
One species donate proton – one species accept proton
Arrhenius acid - substance dissociate in water to produce H+ ions.
Arrhenius base – substance dissociate in water to produce OH- ions.
All Arrhenius acid are Bronsted Lowry acid and water must be present
HCI → H+ + CI-
HCI + H2O ↔ H3O+ + CI-
NaOH → Na+ + OH-
NH3 + H2O ↔ NH4
+ + OH-
CO3
2- + H2O ↔ HCO3
- + OH-
Water/aqueous medium
Water/aqueous medium
Other solvent medium possible
Acid and Bases
Arrhenius acid Arrhenius base
H+ OH-
2
1
Bronsted Base
HPO4
2- + SO3
2- ↔ PO4
3- + HSO3
- HCOOH + CN- ↔ HCOO- + HCN
HCI + H2O ↔ H3O+ + CI-
NH4
+ + CO2
2- ↔ NH3 + HCO3
- CH3COOH + H2O ↔ H3O+ + CH3COO-
Brønsted Acid Brønsted Acid
Brønsted Acid Brønsted Acid
Brønsted Acid Brønsted Acid
Brønsted Acid
Brønsted Acid
Bronsted Base
HF + H2O ↔ F- + H3O+
Bronsted Base
H2PO4
- + OH- ↔ HPO4
2- + H2O
Bronsted Base
H2SO4 + N2H5
+ ↔ HSO4
- + N2H6
2+
Brønsted Acid
Bronsted Base
HCO3
- + H2O ↔ CO3
2- + H3O+

3. Brønsted-Lowry Acid - proton donor - Bronsted-Lowry Base – proton acceptor
Every acid has a conjugate base - Every base has a conjugate acid
Acid donate proton – Base accept proton
Conjugate acid has one more H than base - Conjugate base has one fewer H than acid.
Bronsted Lowry Conjugate acid base pair
HCI + H2O ↔ CI- + H3O+
H2O (base) - H3O+ (conjugate acid)
HCI (acid) - CI- (conjugate base)
CH3COOH + H2O ↔ CH3COO- + H3O+
H2O (base) - H3O+ (conjugate acid)
CH3COOH (acid) - CH3COO- (conjugate base)
HF + H2O ↔ F- + H3O+
H2O (base) - H3O+ (conjugate acid)
HF (acid) - F- (conjugate base)
H2SO4 + N2H5
+ ↔ HSO4
- +N2H6
2+
H2SO4 (acid) - HSO4
- (conjugate base)
N2H5
+ (base) - N2H6
2+(conjugate acid)
HCOOH (acid) - HCOO- (conjugate base)
HCOOH + CN- ↔ HCOO- + HCN
CN- (base) – HCN (conjugate acid)
HPO4
2- + SO3
2- ↔ PO4
3- + HSO3
-
HPO4
2- (acid) - PO4
3- (conjugate base)
SO3
2- (base) - HSO3
- (conjugate acid)
C
O
N
J
U
G
A
T
E
A
C
I
D
B
A
S
E
gain H+
lose H+
gain H+
lose H+
gain H+
lose H+
gain H+
lose H+
gain H+
lose H+
gain H+
lose H+
gain H+
lose H+
Acid + Base ↔ Conjugate Base + Conjugate Acid

4. Bronsted Lowry Conjugate acid base pair
HCOOH (acid) - HCOO- (conjugate base)
HCOOH + CN- ↔ HCOO- + HCN HPO4
2- + SO3
2- ↔ PO4
3- + HSO3
-
HPO4
2- (acid) - PO4
3- (conjugate base)
SO3
2- (base) - HSO3
- (conjugate acid)
NH3 + H2O ↔ NH4
+ + OH-
H2O (acid) - OH- (conjugate base)
NH3 (base) - NH4
+ (conjugate acid)
NH4
+ + CO2
2-↔ NH3 + HCO3
-
NH4
+ (acid) - NH3 (conjugate base)
CO2
2- (base) - HCO3
- (conjugate acid)
NH3 + H2S ↔ NH4
+ + HS- H2PO4
- + OH- ↔ HPO4
2- + H2O
H2PO4
- (acid) - HPO4
2- (conjugate base)
OH- (base) - H2O (conjugate acid)
NH3 (base) - NH4
+ (conjugate acid)
H2S (acid) - HS- (conjugate base)
C
O
N
J
U
G
A
T
E
A
C
I
D
B
A
S
E
Brønsted-Lowry Acid - proton donor - Bronsted-Lowry Base – proton acceptor
Every acid has a conjugate base - Every base has a conjugate acid
Conjugate acid has one more H than base - Conjugate base has one fewer H than acid.
gain H+
lose H+
lose H+
gain H+
CN-(base) - HCN (conjugate acid)
gain H+
lose H+
lose H+
gain H+
lose H+
gain H+
lose H+
gain H+
CH3COOH + H2O ↔ CH3COO- + H3O+
CH3COOH ↔ CH3COO-
H2O ↔ H3O+
Conjugate acid base pair
Conjugate acid base pair
CH3COOH CH3COO-
H2O H3O+
Conjugate acid
Conjugate baseAcid
Base

5. Strong Acid form → Weak Conjugate Base
• Strong acid HCI dissociate completely to form Cl− (weak conjugate base)
• Cl− weak conjugate base won't accept H+ to form back HCI
• HCI + H2O → Cl− + H3O+ (one way)
Bronsted Lowry Conjugate acid base pair
lose H+
gain H+
Acid + Base ↔ Conjugate Base + Conjugate Acid
Brønsted-Lowry Acid - proton donor - Bronsted-Lowry Base – proton acceptor
Every acid has a conjugate base - Every base has a conjugate acid
Acid donate proton – Base accept proton
Conjugate acid has one more H than base - Conjugate base has one fewer H than acid.
Strong acid (HCI) form
weak conjugate base (CI-)
Weak conjugate base (CI) will not accept H+ to form back HCI
Weak Acid form ↔ Strong Conjugate Base
• CH3COOH weak acid dissociate partially, form CH3COO- (strong conjugate base)
• CH3COO- (strong conjugate base) accept H+ to form back CH3COOH molecule.
• CH3COOH + H2O ↔ CH3COO- + H3O+ (reversible)
Weak acid (CH3COOH) form
strong conjugate base (CH3COO-)
Strong conjugate base (CH3COO-) accept H+ form back CH3COOH

6. Bronsted Lowry Conjugate acid base pair
lose H+
gain H+
Acid + Base ↔ Conjugate Base + Conjugate Acid
Brønsted-Lowry Acid - proton donor - Bronsted-Lowry Base – proton acceptor
Every acid has a conjugate base - Every base has a conjugate acid
Acid donate proton – Base accept proton
Conjugate acid has one more H than base - Conjugate base has one fewer H than acid.
Strong base (NaOH) form
weak conjugate acid (H2O)
Weak conjugate acid (H2O) will not lose H+ to form back OH-
Weak base (NH3) form
strong conjugate acid (NH4
+)
Strong conjugate acid (NH4) lose H+ to form back NH3
Strong Base form → Weak Conjugate acid
• Strong base NaOH dissociate completely to form OH-
• OH- strong base dissolve in water form H2O (weak conjugate acid)
• H2O (weak conjugate acid ) will not lose H+ to form back OH-
• OH- + H2O → H2O + OH- ( one way)
Weak Base form ↔ Strong Conjugate Acid
NH3 weak base dissociate partially to form NH4
+ (strong conjugate acid)
NH3 + H2O ↔ NH4
+ + OH-
NH4
+ (strong conjugate acid) lose H+ to form back NH3
NH3 + H2O ↔ NH4
+ + OH- (reversible)

7. Conjugate
Acid
Conjugate
Base
H2SO4 HSO4
HCI CI-
H2SO3 HSO3
-
HF F-
HNO2 NO2
-
CH3COOH CH3COO-
Conjugate
Base
Conjugate
Acid
OH- H2O
PO4
3-
HPO4
2-
CO3
2-
HCO3
-
NH3 NH4
+
Bronsted Lowry Conjugate acid base pair
Strong Base + Acid ↔ Weak Conjugate Acid + Conjugate Base
Strong acid
Weak acid
Weak conjugate base
Strong conjugate base
Strong base
Weak base
Strong conjugate acid
Weak conjugate acid
Strong Acid + Base ↔ Weak Conjugate Base + Conjugate Acid
Weak Acid + Base ↔ Strong Conjugate Base + Conjugate Acid
Weak Base + Acid ↔ Strong Conjugate Acid + Conjugate Base
reversible
reversible
one way
one way
reversible
reversible
reversible

8. H2O (amphiprotic) - act as acid or base
H2O + HCI ↔ H3O+ + CI-
HCO3
- – Base, proton acceptor
HSO4
-
– Base, proton acceptor
Bronsted Lowry Conjugate Acid base pair
H2O – Acid, proton donor H2O – Base, proton acceptor
HCO3
- (amphiprotic) - act as acid or base
HCO3
- – Acid, proton donor
H2O + NH3 ↔ NH4
+ + OH-
HCO3
- + OH- ↔ CO3
2- + H2O HCO3
- + H3O+ ↔ H2CO3 + H2O
HSO4
-
(amphiprotic) - act as acid or base
HSO4
-
– Acid, proton donor
HSO4
- + H2O ↔ H3O+
+ SO4
2-
HSO4
- + HCI ↔ H2SO4 + CI-
Amphiprotic substance :
• Act as acid or base
• Involve only H+.
• Able to donate H+ or gain H+ ions
• All amphiprotic are amphoteric
Amphoteric substance:
• Act as acid or base
• Does not involve only H+ ions
• Al2O3 is amphoteric – No H+ ions
• Al2O3 (base) + 6HCI → 2AICI3 + 3H2O
• AI2O3 (acid) + 2NaOH + 3H2O → 2NaAl(OH)4
amphiprotic
amphoteric
gain H+lose H+
lose H+
lose H+
gain H+
gain H+
H+
Amphiprotic – Proton donor (acid)
- Proton acceptor (base)

9. SO2 accept e- CO2 accept e-
Lewis acid Lewis base
CO2 + H2O → H2CO3
H2O donate e-
Lewis acid Lewis base
H2O donate e-
Lewis Acid/Base
Lewis Acid - substance accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance donate electron/lone pair electron donor
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair
Lewis Acid Lewis Base
LIKE electron (-ve)
Electron deficient – accept lone pair
LIKE nucleus (+ve)
Electron rich – donate lone pair
NO2
+ Br+SO2 CO2
SO2 + H2O → H2SO3
Molecule as
Lewis Acid/Base
Molecule acting as Lewis Acid Molecule /Ions as Lewis Base

10. Lewis Acid/Base
H2O donate e-
HCI + :H2O → CI- + H3O+
HCI accept e-
Lewis acid Lewis base
BF3 + :NH3 → BF3 – NH3
Molecule as
Lewis Acid/Base
Lewis acid Lewis base
HF accept e-
Lewis acid
HF + H2O → F- + H3O+
H2O donate e-
Lewis baseLewis acid
Lewis Acid - substance accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance donate electron/lone pair electron donor
Lewis Base - donate electron pair form dative/coordinate bond with Lewis acid
Molecule as
Lewis Acid/Base
H+ transfer
Dative bond
Dative bond
Dative bond
Electron
donor
Electron
acceptor
Electron
acceptor
Electron
donor
Electron Acceptor
Electron Deficient
Electron donor
Electron donorElectron Acceptor
Electron Deficient
NH3 donate e-
BF3 accept e-
F F-
No H+ transfer
BF3 + :F → BF4
F donate e-
BF3 accept e-
:F :F
Dative bondLewis base

11. SO2 + H2O → H2SO3
SO2 accept e- CO2 accept e-Molecule as
Lewis Acid/Base
Lewis acid Lewis base
Lewis baseLewis acid
H2O + :O2- → 2OH-
O2- donate e-
H2O accept e-
Lewis acid Lewis base
CH3COOH accept e-
CO2 + H2O → H2CO3
H2O donate e-
Lewis acid Lewis base
H2O donate e-
CH3COOH + H2O ↔ CH3COO- + H3O+
H2O donate e-
Lewis Acid/Base
Molecule as
Lewis Acid/Base
Lewis Acid - substance accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance donate electron/lone pair electron donor
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair

12. Ligand as Lewis Base
• lone pair electron
• dative bond with metal
Lewis Acid/Base
Lewis Acid - substance accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance donate electron/lone pair electron donor
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair
Lewis Acid Lewis Base
LIKE electron (-ve)
Electron deficient – accept lone pair
LIKE nucleus (+ve)
Electron rich – donate lone pair
Cu2+
Metal Ion as Lewis Acid
•high charge density
• empty 3d orbitals
Ni2+ AI3+ Fe3+
Cu2+ + :6H2O → [Cu(H2O)6]2+
Cu2+
accept e-
Metal Ion as Lewis Acid
Ligand as Lewis BaseH2O donate e-
Lewis acid
Co2+ + :4CI- → [Co(CI)4]2-
CI- donate e-
Lewis base Lewis acid Lewis base
C02+
accept e-
Co2+

13. Metal Ion as Lewis Acid
Ligand as Lewis Base
Lewis baseLewis acid
Fe3+ + :SCN- → [FeSCN]2+
SCN- donate e-
Fe3+
accept e-
H2O donate e-
Fe3+ + 6H2O → [Fe(H2O)]3+
Lewis acid Lewis base
Fe3+
accept e-
AI(OH)3 + :OH-
→ AI(OH)4
-
OH- donate e-
AI3+
accept e-
Lewis baseLewis acid
Ni2+ + :6NH3 → [Ni(NH3)6]2+
NH3 donate e-
Ni2+
accept e-
Lewis baseLewis acid
Lewis Acid/Base
Metal Ion as Lewis Acid
Ligand as Lewis Base
Lewis Acid - substance accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – substance donate electron/lone pair electron donor
Lewis Base - donate electron pair form dative/coordinate bond with Lewis acid
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair

14. Brønsted-Lowry Acid - substance that donate proton/proton donor
Bronsted-Lowry Base – substance that accept proton/proton acceptor
One species donate proton – one species accept proton
Arrhenius acid - substance dissociate in water to produce H+ ions.
Arrhenius base – substance dissociate in water to produce OH- ions.
All Arrhenius acid are Bronsted Lowry acid and water must be present
HCI → H+ + CI-
HCI + H2O ↔ H3O+ + CI-
NaOH → Na+ + OH-
NH3 + H2O ↔ NH4
+ + OH-
CO3
2- + H2O ↔ HCO3
- + OH-
Water/aqueous medium
Water/aqueous medium
Other solvent medium possible
Definition of Acid and Bases
Arrhenius acid Arrhenius baseH+ OH-
2
1
gain H+
Acid + Base ↔ Conjugate Base + Conjugate Acid
lose H+
HCI (acid) - CI- (conjugate base)
H2O (base) - H3O+ (conjugate acid)
HCI + H2O ↔ CI- + H3O+
Lewis Acid - accept electron/electron acceptor, empty orbital/electron deficient
Lewis Base – donate electron/lone pair electron donor.
Lewis Base - donate electron pair form dative/coordinate bond with Lewis acid
3
HCI + H2O → CI- + H3O+
H2O donate e-HCI accept e-
Lewis acid Lewis base
gain H+
lose H+
Metal Ion as Lewis Acid
• electron acceptor
• high charge density
• empty 3d orbitals
Ligand as Lewis Base
• electron donor
• lone pair electron
• dative bond with metal
Lewis acid – electrophile
Lewis base - nucleophile
Donation/acceptance electron pair

15. For following species, state whether it behave as Lewis acid or Lewis base
a) PH3
b) BCI3
c) H2S
d) SF4
e) Cu2+
a) PH3 – P (gp 5) - 1 lone pair electron – electron donor – Lewis base
b) BCI3 – B (gp 3) - electron deficient/incomplete valence shell – electron acceptor – Lewis acid
c) H2S – S (gp 6) - 2 lone pair electron – electron donor – Lewis base
d) SF4 – S (gp 6) - 1 lone pair electron – electron donor – Lewis base
e) Cu2+
- (transition metal) – high charge density/incomplete 3d orbital – electron acceptor – Lewis acid
Question Answer
IB Questions
Which acid/base rxn is Lewis Theory and Bronsted Theory?
A) NH3 + HCI ↔ NH4CI B) H2O + H2O ↔ H3O+ + OH- C) Cu2+ + 4NH3 ↔ [Cu(NH3)4]2+ D) BaO + H2O ↔ Ba2+ + 2OH-
A) NH3 + HCI ↔ NH4CI B) H2O + H2O ↔ H3O+ + OH- C) Cu2+ + 4NH3 ↔ [Cu(NH3)4]2+ D) O2- + H2O ↔ 2OH-
Bronsted Theory Bronsted Theory Lewis Theory Bronsted Theory
(H+ transfer) (H+ transfer) (NO H+ transfer) (H+ transfer)
H+
H+ H+
Identify Lewis acid and Lewis base
2
1
3
A) Zn2+ + 4NH3 → [Zn(NH3 )4 ] 2+ B) 2CI - + BeCI2 → [BeCI4]2- C) Mg2+ + 6H2O → [Mg(H2O)6]2+
Lewis acid
Lewis acid
Lewis acid
Lewis base Lewis base
Lewis base

16. Lewis Acid/Base
Definition of Acid and Bases
Bronsted – Lowry
Acid/Base
Arrhenius Acid/Base
Arrhenius acid/base
• Limited/narrow definition
• Only water medium
• Substance must have H atom
Bronsted Lowry acid/base
• Broader definition
• Proton donor/acceptor
• Other medium
• Substance must have H atom
Lewis acid/base
• Broadest definition
• Electron acceptor/donor
• Substance doesn’t need to have H
All Arrhenius acid are Bronsted Lowry acid All Bronsted Lowry acid are Lewis acid
Click here Bronsted Lowry , Lewis Acid/Base
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3
1
2
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