Acids, Bases and Salts

Acid – An acid is a chemical material which exhibits following properties –

Sour in taste; when sprinkled on a blue litmus paper, turns it red; contains replaceable hydrogen; gives out hydrogen ion H+ in Aqueous Solution according to Arrhenius Theorem; can donate a proton According to Bronsted Lowry concept and can accept electrons according to Lewis Concept

Uses of Acid- Acids are of different types. Some of the most common types of some common acids are given here-

Vinegar, used in the kitchen, is a liquid containing 3-6% acetic acid. It is used in pickles and in many food preparations.

Lemon and orange juice contains citric acid. Citric acid is used in the preparation of effervescent salts and as a food preservative.

Acids have been put to many uses in industry. Nitric acid and sulphuric acid are used in the manufacture of fertilizers, dyes, paints, drugs and explosives.

Sulphuric acid is used in batteries, which are used in cars, etc. Tannic acid is used in the manufacture of ink and leather.

Hydrochloric acid is used to make aqua regia, which is used to dissolve noble metals such as gold and platinum.

Sulphuric acid is used in manufacturing fertilizers such as super phosphate, ammonium sulpahte etc. 


Strong Acids

Strong acids completely dissociate in water, forming H+ and an anion. There are six strong acids. The others are considered to be weak acids.

Examples of Strong Acids

HCl - hydrochloric acid
HNO3 - nitric acid
H2SO4 - sulfuric acid
HBr - hydrobromic acid
HI - hydroiodic acid
HClO4 - perchloric acid

Weak Acids

A weak acid only partially dissociates in water to give H+ and the anion. Examples of weak acids include hydrofluoric acid, HF, and acetic acid, CH3COOH. Weak acids include:

Molecules that contain an ionizable proton. A molecule wih a formula starting with H usually is an acid.
Organic acids containing one or more carboxyl group, -COOH. The H is ionizable.
Anions with an ionizable proton. (e.g., HSO4- → H+ + SO42-)
Cations
transition metal cations
heavy metal cations with high charge
NH4+ dissociates into NH3 + H+

Uses of Some Most Common Types of Acids

Uses of HCl- Hydrochloric acid contributes to proper digestion, but it also has common applications. Hydrochloric acid is used in the production of chlorides, dyes, fertilizers and in various industries such as photography, textiles and rubber. HCl also used as laboratory agent.

Uses of Nitric Acid chemical formula HNO3
The important uses of nitric acid are:
1 Nitric acid plays a significant role in the manufacture of various products such as:

Explosives like trinitrotoluene (T.N.T.) nitro glycerine, cotton, nal etc.
Fertilizers such as calcium nitrate, nium nitrate etc.
Nitrate salts such as calcium nitrate, silver nitrate, nium nitrate.
Dyes, perfumes, etc. from coal tar products.
Sulphuric acid by Lead Chamber process.

2 It is used in the purification of silver, gold, platinum etc.
3 Nitric acid is used in etching designs on copper, brass, bronze ware etc.
4 It is used to prepare "aqua regia" to dissolve the noble elements.
5 It is used as a laboratory reagent.

Uses of Boric Acid chemical formula H3BO3

Boric acid can be used as an antiseptic for minor burns or cuts.
Boric acid is used as insecticide for control of cockroaches, termites, fire ants, fleas, silverfish, and many other insects.
Boric Acid is used in combination with an ethylene glycol carrier to treat external wood against fungal and insect attack.
Concentrates of borate-based treatments can be used to prevent slime, mycelium and algae growth, even in marine environments.
Boric acid is used in nuclear power plants as a neutron poison to slow down the rate at which fission is occurring.
Boric acid is used in the manufacture of monofilament fiberglass.
It is used in pyrotechnics to prevent the amide-forming reaction between aluminium and nitrates. A small amount of boric acid is added to the composition to neutralize alkaline amides that can react with the aluminium.

Base- A base is a substance that can accept hydrogen ions (protons) or more generally, donate a pair of valence electrons. A soluble base is referred to as an alkali if it contains and releases hydroxide ions (OH−) quantitatively.

Properties of Bases

Some general properties of bases are defined here-

Slimy or soapy feel on fingers, due to saponification of the lipids in human skin.
Concentrated or strong bases are caustic on organic matter and react violently with acidic substances.
Aqueous solutions or molten bases dissociate in ions and conduct electricity.
Reactions with indicators: bases turn red litmus paper blue, phenolphthalein pink, keep bromothymol blue in its natural colour of blue, and turns methyl orange yellow.
The pH level of a basic solution is higher than 7.
Bases are bitter in taste.

The pH value

The pH value is a measure of the activity of the (solvated) hydrogen ion. p[H], which measures the hydrogen ion concentration is closely related to, and is often written as, pH.Pure water has a pH very close to 7 at 25°C. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline.

The pH value of some common liquids

Table

0 - Hydrochloric Acid (HCl)
- Battery Acid (H2SO4 sulfuric acid)
- Lemon Juice
2.2 - Vinegar
- Apples
- Wine and Beer
4.5 - Tomatoes
- Milk
7.0 - Pure Water
7.4 - Human Blood
8.3 - Baking Soda (Sodium Bicarbonate)
10.5 - Milk of Magnesia
11.0 - Ammonia
12.4 - Lime (Calcium Hydroxide)
13.0 - Lye
14.0 - Sodium Hydroxide (NaOH)


Salt-A salt is farmed when and acid reacts with a base. The chemical reaction occurs as

Acid + Base ==========> Salt + Water

For example –

HCl + NaOH ==========> NaCl + H2O


Use of some important salts

Sodium Chloride – Used as flavoring in food. In saline water to treat patients of dehydration, 0.9 % NaCl is used, and in the preparation of HCl etc

Sodium Iodate – Iodized salt to prevent Goitre disease.

Sodium Carbonate – As washing soda, manufacturing of glass etc.

Sodium Benzoate – As a food preservative for pickles.

Potassium Nitrate – As a fertilizer, in gun powder and in match sticks.

Calcium Chloride – Dehydrating agent used for removing moisture from gases.

Calcium Carbonate / Lime Stone – In building construction, and extraction of metals

Calcium Sulphate – Used as Plaster of Paris molecular formula 2CaSO4 H2O for moulds and statues and in the Cement industry in the form of Gypsum CaSO4 H2O.

Calcium Phosphate – As a fertilizer (superphosphate of lime)

Bleaching Powder – As disinfectant; as bleaching agent for removing colors.

Alum (Potassium Aluminium Sulphate)- In the purification of water, in the dying industry and as antiseptic.

The Acidic and Basic Nature of Some Household Materials

Acidic – Bathroom Acid; Vitamin C Tablets; Lemon Juice; Orange Juice; Tomato Juice; Vinegar; Fizzy Drinks like Colas and Sodawater

Basic- Milk of Magnesia / Anta Acids; Toothpaste; Soap; Washing Soda, Slaked Lime