Acids, Bases and Salts
Introduction to Acids, Bases and Salts
Classification of matter
On the basis of
a) composition - elements, compounds and mixtures
b) state - solids, liquids and gases
c) solubility - suspensions, colloids and solutions
Types of mixtures - homogeneous and heterogeneous
Types of compounds - covalent and ionic
What Is an Acid and a Base?
Ionisable and non-ionisable compounds
An ionisable compound when dissolved in water or in its molten state, dissociates into ions
almost entirely. Example: NaCl, HCl, KOH, etc.
A non-ionisable compound does not dissociate into ions when dissolved in water or in its
molten state. Example: glucose, acetone, etc.
Arrhenius theory of acids and bases
Arrhenius acid - when dissolved in water, dissociates to give H (aq) or H
+
3O
+
ion.
Arrhenius base - when dissolved in water, dissociates to give OH ion.
−
Examples
Acids
Hydrochloric acid (H Cl)
Sulphuric acid (H2 SO4 )
Nitric acid (H N O 3)
Bases
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide (Ca(OH ) 2)
Bronsted Lowry theory
, A Bronsted acid is a H +
(aq) ion donor.
A Bronsted base is a H +
(aq) ion acceptor.
Example
In the reaction: H Cl(aq) + N H 3 (aq) → NH
+
4
(aq) + Cl
−
(aq)
H Cl - Bronsted acid and Cl - its conjugate acid
−
N H3 - Bronsted base and N H - its conjugate acid
+
4
Physical test
Given are two possible physical tests to identify an acid or a base.
a. Taste
An acid tastes sour whereas a base tastes bitter.
The method of taste is not advised as an acid or a base could be contaminated or corrosive.
b. Effect on indicators by acids and bases
An indicator is a chemical substance which shows a change in its physical properties,
mainly colour or odour when brought in contact with an acid or a base.
Below mentioned are commonly used indicators and the different colours they exhibit:
a) Litmus
In neutral solution - purple
In acidic solution - red
In basic solution - blue
Litmus is also available as strips of paper in two variants - red litmus and blue litmus.
An acid turns a moist blue litmus paper to red.
A base turns a moist red litmus paper to blue.
b) Methyl orange
In neutral solution - orange
In acidic solution - red
In basic solution - yellow
c) Phenolphthalein
In neutral solution - colourless
In acidic solution - remains colourless
In basic solution - pink
Acid Base Reactions
Introduction to Acids, Bases and Salts
Classification of matter
On the basis of
a) composition - elements, compounds and mixtures
b) state - solids, liquids and gases
c) solubility - suspensions, colloids and solutions
Types of mixtures - homogeneous and heterogeneous
Types of compounds - covalent and ionic
What Is an Acid and a Base?
Ionisable and non-ionisable compounds
An ionisable compound when dissolved in water or in its molten state, dissociates into ions
almost entirely. Example: NaCl, HCl, KOH, etc.
A non-ionisable compound does not dissociate into ions when dissolved in water or in its
molten state. Example: glucose, acetone, etc.
Arrhenius theory of acids and bases
Arrhenius acid - when dissolved in water, dissociates to give H (aq) or H
+
3O
+
ion.
Arrhenius base - when dissolved in water, dissociates to give OH ion.
−
Examples
Acids
Hydrochloric acid (H Cl)
Sulphuric acid (H2 SO4 )
Nitric acid (H N O 3)
Bases
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide (Ca(OH ) 2)
Bronsted Lowry theory
, A Bronsted acid is a H +
(aq) ion donor.
A Bronsted base is a H +
(aq) ion acceptor.
Example
In the reaction: H Cl(aq) + N H 3 (aq) → NH
+
4
(aq) + Cl
−
(aq)
H Cl - Bronsted acid and Cl - its conjugate acid
−
N H3 - Bronsted base and N H - its conjugate acid
+
4
Physical test
Given are two possible physical tests to identify an acid or a base.
a. Taste
An acid tastes sour whereas a base tastes bitter.
The method of taste is not advised as an acid or a base could be contaminated or corrosive.
b. Effect on indicators by acids and bases
An indicator is a chemical substance which shows a change in its physical properties,
mainly colour or odour when brought in contact with an acid or a base.
Below mentioned are commonly used indicators and the different colours they exhibit:
a) Litmus
In neutral solution - purple
In acidic solution - red
In basic solution - blue
Litmus is also available as strips of paper in two variants - red litmus and blue litmus.
An acid turns a moist blue litmus paper to red.
A base turns a moist red litmus paper to blue.
b) Methyl orange
In neutral solution - orange
In acidic solution - red
In basic solution - yellow
c) Phenolphthalein
In neutral solution - colourless
In acidic solution - remains colourless
In basic solution - pink
Acid Base Reactions
