Acids, Bases and Salts.

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 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


lonisable and non-ionisable compounds

An ionisable compound when dissolved in water or in its molten state,

dissociates into ions almost entirely. Example: NaCl, HCI, KOH, etc. A non-lonisable 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 H0 ion Arrhenius base - when dissolved in water; dissociates to give OH ion.


Examples:


Acids


Hydrochloric acid (HCI)

Sulphuric acid (H₂50₁)

Nitric acid (HNO₂)

Bases

Sodium hydroxide (NaOH)

Potassium hydroxide (KOH)

Calcium hydroxide (Ca(OH):)


Bronsted Lowry theory

A Bronsted and is a H(aq) londonor.

A Bronsted base is a H(aq) ion acceptor.


Example


In the reaction: HCl(aq) + NH₂(aq) + NH(aq) + Cl(aq)

MCI - Bronsted acid and C-its conjugate acid

NH,- Bronsted base and NH₂ - its conjugate acid


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