This video discuss about bronsted lowry concept of acid and base. Conjugate acid base pairs, relative strength of acid base, Advantages & Limitations bronsted lowry concept of acid and base and Examples of Acid base reactions.

1. Chemistry Class 12
3. IONIC EQUILIBRIA
Part-3
Bronsted –Lowry Theory
of
Acids and Bases
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3. 3.3.2 Bronsted-Lowry theory
According to Bronsted-Lowry theory(1923)
Acid :- Acid is the substance that donates proton H+ to another
substance.
Base :- Base is a substance that accept proton H+ from another
substance. e.g.
HCl + NH3 NH4
+ + Cl –
Acid-1 Base-2 Acid-2 Base-1
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4. HCl + NH3 NH4
+ + Cl –
Acid-1 Base-2 Acid-2 Base-1
HCL and NH4
+ are proton donor .Act as acids
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5. HCl + NH3 NH4
+ + Cl –
Acid-1 Base-2 Acid-2 Base-1
Ammonia and chloride ion are proton acceptor.
Act as bases.
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6. Arrhenius acids are also Bronsted acids. But Arrhenius bases
are not Bronsted bases.
1. HCL(aq)+ H2O(l) H3O+ + Cl- (aq)
acid 1 base2 acid 2 base1
2. NH3 (aq) + H2O(l) NH4
+(aq) + OH-(aq)
base2 acid 1 acid 2 base1
3. H2O(l) + CO3
2-(aq) HCO3
-(aq) + OH-(aq)
acid 1 base2 acid 2 base1
4. NH4
+(aq) + H2O(l) H3O+(aq) + NH3(aq)
acid 1 base2 acid 2 base1
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7. Products of the Bronsted –Lowery acid base reactions are acids and
bases.
A pair of an acid and a base differing by proton is said to be a conjugate
acid –base pair.
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9. The base produced by accepting the proton from an acid is the
conjugate base of that acid.
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10. The acid produced when base accepts a proton is called
conjugate acid of that base.
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Write the conjugate acids for Bronsted –Lowery conjugate base
Bronsted –Lowery base Bronsted –Lowery conjugate acid
NH2
-
H2PO4
-
NH3
H3PO4

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Write the conjugate acids for Bronsted –Lowery conjugate base
Bronsted –Lowery acid Bronsted –Lowery conjugate base
HCN
H2O
CN-
OH-

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❖ Points to be remember
❖ Acid= conjugate base + H+
❖ Base + H+ = conjugate acid
❖ Each conjugate acid has one extra proton.
❖ Each conjugate base has one proton less.

14. Strengths of conjugate Acids and Bases
The strength of an acid depends upon its tendency to donate
proton and strength of base depends upon its tendency to
accept proton .
Strong acid –good proton donor
Strong base – good proton acceptor.
1. HCL(aq) + H2O(l) H3O+ (aq) + Cl- (aq)
Strong acid 1 base2 acid 2 weak base1
2.CH3COOH + H2O(l) CH3COO- (aq) + H3O+ (aq)
weak acid 1 strong base
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❖ Points to be remember
Strong acid has weak conjugate base.
Weak acid has strong conjugate base
Strong base has weak conjugate acid.
Weak base has strong conjugate acid.

16. Advantages of Bronsted –Lowery concept:-
1)This concept explain basic characters of substances like Na2CO3, NH3
.
2) This concept is not limited to molecules but explain acidic and basic
characters of ionic species.
3) It can explain acid base reaction in the non aqueous medium.
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17. Bronsted –Lowery concept fails to explain:-
1)Acidic substances which do not have proton e.g ALCl3 , BF3
2)Reaction between acidic oxides and basic oxides.
CaO + SO3 → CaSO4
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18. THANK YOU
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