ACID,BASE AND SALT

By Fawad Mueen Arbi

According to Arrhenius Concept : Acid is a substance that dissociates in aqueous

solution to give hydrogen ions. HA H+ + A- According to Bronsted-Lowry Concept : An Acid is a substance (molecule or ion) that can

donate Proton (H+) to another substance. According to Lewis Concept : An Acid is a substance which can accept a pair of

electrons.

1. ACID

Properties of Acids : Acids have sour taste. For example, unripe

citrus fruits or lemon juice. They turn blue litmus red. They are corrosive in concentrated form. Their aqueous solutions conduct electricity.

Names and formulae of some important acids are as follows :

Name of Acids Formulae

1. Hydrochloric Acid HCl

2. Sulphuric Acid H2SO4

3. Phosphoric Acid H2PO4

4. Nitric Acid HNO3

Uses of Acids : Sulphuric acid is used to manufacture fertilizers, ammonium

sulphate, explosives, paints, drugs and drugs.

Nitric acid is used in manufacturing of fertilizers, explosives, paints and drugs etc.

Hydrochloric acid is used for cleaning metals, tanning and in printing press

Benzoic acid is used for food preservation.

Acetic acid is used for flavoring food and food flavouring.

2. Base According to Arrhenius Concept : A Base is a substance which dissociates in

aqueous solution to give hydroxide ions

BOH B+ + OH-

According to Bronsted-Lowry Concept : A Base is a substance that can accept (H+)

from another substance. According to Lewis Concept : A Base is a substance (molecule or ion)

which can donate a pair of electrons.

Uses of Bases : Sodium Hydroxide is used for manufacturing soap

Calcium Hydroxide is used for manufacturing of bleaching powder, softening of hard water and neutralization.

Potassium Hydroxide is used in alkaline batteries.

Magnesium Hydroxide is used as a base to neutralize acidity in stomach.

Aluminium Hydroxide is used as a foaming agent in fire extinguishers.

Ammonium Hydroxide is used to remove grease stains from cloths.

Table Base which recognizably :

Names of Bases Chemical Formulae

1. Sodium Hydroxide NaOH

2. Potassium Hydroxide

KOH

3. Calcium Hydroxide Ca(OH)2

4. Aluminium Hydroxide

Al(OH)3

3. Salt Salts are ionic compounds generally formed by the

neutralization of acid with a base.

Salts are made up of positive and negative ions.

Its general equation is as follows:

Acid + Base Salt + Water

For Example :

HCl + NaOH NaCl + H2O

Types of Salts :

Normal Salts

Acidic Salts

Basic Salts

Double Salts

Mixed Salts

Complex Salts

Besides produce from react between acid and base . Salt also could produce from reaction others , namely :

1. Base + Metallic Oxide Salt + Water

2. Acid + Metallic Oxide Salt + Water

3. Oxide Acid + Oxide Base Salt

4. Metal + Acid Salt + Hydrogen

Uses of Salts : Sodium Chloride(NaCl) is commonly used as a table salt and for cooking

purposes. It is also used for de-icing roads in winter.

Sodium Carbonate/Soda Ash(Na2CO3) is used for the manufacture of glass, detergents, pulps and paper etc.

Sodium Carbonate/Washing Soda(Na2CO3.10H2O) is used as cleaning agent for domestic and commercial purposes, for softening of water, in manufacture of chemicals

Sodium Sulphate(Na2SO4) It is used for the manufacture of glass, paper and detergents.

Sodium Silicate(Na2SiO3) It is used for manufacturing of detergents, cleaning agents and adhesives

Sodium Chlorate(NaClO3) It is used for manufacture of explosives plastics and other chemicals.

Calcium Chloride(CaCl2) It is used for de-icing roads in winter, as a drying agent and as freezing agent.

Potassium Nitrate(KNO3) It is used for fertilizer and for the manufacture of flint glass.

pH Scale : pH is a measure of hydrogen ion concentration; a measure of

the acidity or alkalinity of a solution. Aqueous solutions at 25°C with a pH less than seven are acidic, while those with a pH greater than seven are basic or alkaline. A pH level of is 7.0 at 25°C is defined as 'neutral‘.

pH is the negative logarithm of molar concentration of Hydrogen ions.

pH = -log[ H+ ]

with reference to this equation , a scale develops to the molar concentration of H+ ions that is called pH scale.

A pH scale is shown below :

Indicators :

Indicators are organic compounds. They have Different colours in acidic and alkaline solutions.

Litmus is a common indicator

Red Litmus Turns blue in base

Blue Litmus Turns red in acid

Each indicator has a specific colour in acidic medium which changes at specific pH to another colour in basic medium.

THANK YOUANY QUESTION ?