An acid is defined as a substance that yields hydrogen ions in water, while a base yields hydroxide ions. The Arrhenius theory defines acids and bases in terms of their dissociation in water, but it is limited to aqueous solutions and does not account for bases like ammonia without hydroxide groups. Lewis expanded the definitions to include any species that can accept or donate electron pairs. Acids and bases can be strong or weak depending on how fully they dissociate in water, yielding more or fewer hydrogen or hydroxide ions. A salt is formed when an acid is neutralized by a base through ionic bonding, and salts exist as neutral or acidic/basic depending on remaining hydrogen or hydroxide

3. → An acid can be defined as a substance that yields hydrogen
ion (H+) when dissolved
in water.
→ A Base can be defined as a substance that yields hydroxide
ion (OH−) when dissolved in water.
Arrhenius Acid → HCl(aq) ⇌ H+ + Cl−
Arrhenius Base → NaOH(aq) ⇌ Na+ + OH−

4. Arrhenius theory of acids and bases are
limited, they apply only to water
solutions and it also does not account
for the basicity of ammonia (NH3) that
doesn’t contain (OH) group.

5. An acid is a substance, having a tendency to
donate one or more protons
A base is a substance, having a tendency to
accept (add) one or more protons

7. Lewis Acid → An acid is any species
(molecule or ion) which can accept a pair of
electrons.
Lewis Base → A base is any species
(molecule or ion) which can donate a pair
of electrons

11. The number of replaceable or ionizable hydrogen atoms present in a
molecule of an acid is called “Basicity of an acid”
➢ Mono means one and protic means proton (Mono-protic acid)
H+-Cl− + H+-OH− → H3O+ + Cl−
➢ Di means two and protic means proton (Di-protic acid)
H2SO4 + H2O → H3O+ + HSO4
−
HSO4
− + H2O → H3O+ + SO4
−2
➢ Tri means three and protic means proton (Tri-protic acid)
H3PO4 + H2O → H3O+ + H2PO4−
H2PO4− + H2O → H3O+ + HPO4
−2
HPO4
−2 + H2O → H3O+ + PO4
−3

12. Strong Acid:- An acid that yield large number of
hydrogen ions (H+) in aqueous solution is said to be
strong acid.
Example:- HCl, HBr, HI, H2SO4, H3PO4 (Strong
electrolytes and acids)
Weak Acid:- An acid dissociate to a small extent in
water to yield (H+) is said to be weak acid.
Example:- HF, H2CO3, HCOOH

13. Strong Base:- A base that yields large number of hydroxide ions
(OH−) in aqueous solution is said to be strong base.
Example:- NaOH, KOH, Ba(OH)2 , Ca(OH)2 (Strong electrolytes
and bases)
Weak Base:- A base dissociate to a small extent in water to
yield (OH−) is said to be weak base.
Example:- Mg(OH)2 , NH4OH , Be(OH)2

14. ❖ Acidic Solution:- When the concentration of hydrogen ion (H+) is
greater than the concentration of hydroxide ion (OH) is called
acidic solution.
❖ Basic Solution:- When the concentration of hydroxide ion (OH−) is
greater than the concentration of hydrogen ion (H+) is called basic
solution
❖ Neutral Solution:- When the concentration of hydrogen ion (H+) is
equal the concentration of hydroxide ion (OH−) is called neutral
solution.

15. A salt is a ionic compound to produce when
an acid neutralized by a base.
Example:-
NaOH + HCl → NaCl + H2O

17. Salts which are formed by the complete
neutralization of an acid by a base.
Example
NaCl, NaNO3, K2SO4
(These salts do not have replaceable hydrogen
atom or hydroxyl groups)

18. Salts which are formed by the partial
neutralization of an acid by a base.
Example
NaHSO4 , KHCO3, KHSO4
(These salts contain replaceable hydrogen ion)

19. Salts which are formed by the partial
neutralization of a base by an acid.
Example
Mg(OH)Cl, Zn (OH)Cl, Ca(OH)Br
(These salts have replaceable hydroxyl
groups)

20. The crystalline compounds which are obtained, when to
specific salts are crystallized together are known as
double salts.
Example:-
- Potash Alum → K2SO4 . Al2(SO4)3 . 24H2O
- Chrome Alum → K2SO4 . Cr2(SO4)3 . 24H2O
- Carnalite → KCl . MgCl2 . 6H2O
- Mohr’s Salt → FeSO4 . (NH4)2 SO4 . 6H2O

21. A substance (such as water) that can behave both an acid and base
is said to be an amphoteric substance.
Example
Acid + Base ⇌ Acid + Base
HCl + H2O ⇌ H3O + Cl−
H2O + NH3 ⇌ NH4 + OH−