Introduction of Acid, Base & Salt

1. Water, Acid, Base & Salt
BIOCHEMISTRY_PAPER_1
HAMDARD UNIVERSITY BANGLADESH
MD. ABDUL MANNAN
Bachelor of Unani Medicine & Surgery (DU)
MS in Microbiology (SU), BMT-Laboratory Medicine (DU)
MS Biotechnology & Genetic Engineering, MCSW (DU)
Assistant Professor

2. IONIZATION OF WATER
Water, even pure water, has an amphiprotic nature. This means
that a small amount of ions will form in pure water. Some
molecules of H2O will act as acids, each donating a proton to a
corresponding H2O molecule that acts as a base. Thus, the
proton-donating molecule becomes a hydroxide ion (OH-),
while the proton-accepting molecule becomes a hydronium
ion (H3O+).
Water molecules can function as both acids and bases. One
water molecule (acting as a base) can accept a hydrogen ion
from a second one (acting as an acid). This will be happening
anywhere there is even a trace of water - it does not have to be
pure. A hydronium ion and a hydroxide ion are formed.

3. IONIZATION OF WATER
However, the hydroxonium ion is a very strong acid, and the hydroxide
ion is a very strong base. As fast as they are formed, they react to
produce water again. The net effect is that an equilibrium is set up.
2 H2O (l) ⇌ H3O+ (aq) + OH− (aq)

4. Acid & Classification
Acid:
An acid is a substance which donate hydrogen ion (H+)
when dissolved in water.
Example: H2CO3, HCl, H2SO4.
Classification of Acid:
A. According to the dissociation capacity:
1. Strong acids. Example: H2SO4, HCl.
2. Weak acids. Example: H3PO4, H2CO3.
B. According to the composition:
1. Oxy acids. Example: H2SO4, HNO3, H3PO4.
2. Hydra acids. Example: HCl, HCN, H2S.
C. According to the source:
1. Organic acids. Example: CH3COOH, HCOOH.
2. Inorganic acids. Example: H2SO4, HNO3, H3PO4.
D. According to the presence of base:
1. Mono-basic acids. Example: HCl, HNO3
2. Di-basic acids. Example: H2SO4 , H2CO3
3. Tri-basic acids. Example: H3PO4

5. Difference between strong acid & weak acid
Strong acid weak acid
Acid which are almost
completely dissociated in
water are called strong acid.
Acid which are poorly
dissociated in water are called
strong acid.
Strong acid dissociate
quickly.
Weak acid dissociates slowly.
Its conjugated base is weak. Its conjugated base is strong.
It is irreversible in reaction. It is reversible in reaction.
Usually they are inorganic
acid.
Usually these are organic are
organic acid.
Example: HCl, H2SO4 Example: H2CO3, CH3COOH

6. Base & Classification
Base:
A base is any metal oxide or hydroxide that react with an
acid to give salt and water.
A base is a substance that can accept hydrogen ions (H+)
in a solution is called base. Example: NaOH, KOH.
Classification of base:
1. Soluble base. (Alkali)
2. Insoluble base. (Metal oxide or hydroxide )
Conjugate base:
Conjugate base is a substance which is formed when an
acid loses a hydrogen ion (H+) and it can reform into
acid when by gaining a hydrogen ion (H+).
Alkali: An alkali is a base that is soluble in water.
Example: NaOH, KOH, Mg(OH)2.

7. Difference between acid & base/alkali
Acid Alkali / Base
1. It produces hydrogen ion
(H+) in water.
1. It produces hydroxyl ion
(OH-) in water.
2. It produces salt and water
with alkali.
2. It produces salt and water
with acid.
3. It converts blue litmus into
red litmus.
3. It converts red litmus into
blue litmus.
4. It is sour in taste. 4. It is bitter in taste.
5. Examples: HCl, H2SO4. 5. Examples: NaOH, KOH.

8. Salt & classification of salt
Salt:
Salts may be defined as the ionic compounds produce by
the neutralization reaction of an acid and a base.
Example: NaCl, KCl
They are composed of cations and anions so that salt is
electrically neutral.
Classification of salt:
1. Normal salt. Example: NaCl, KCl
2. Acidic salt. Example: NaHCO3, NH4HSO4.
3. Basic salt. Example: CuCO3, Cu(OH)2

9. Properties of acid
1. It produces hydrogen ion (H+) in aqueous solution.
2. It produces salt and water with alkali.
3. It converts blue litmus into red litmus.
4. It is sour in taste.
1. It can neutralize acid and acidic oxide.
2. It produces salt and water with acid.
3. It converts red litmus into blue litmus.
4. It is bitter in taste.
1. It produces hydroxyl ion (OH-) in aqueous solution.
2. It produces salt and water with acid.
3. It converts red litmus into blue litmus.
4. It is bitter in taste.
Properties of base
Properties of alkali