Category: 3. Salt Properties and Examples

When an electric current is passed through a strong solution of salt in water, electrolysis occurs and three products are formed:

• Chlorine (Cl₂)
• Sodium hydroxide (NaOH)
• Hydrogen (H₂).

Because hydrogen and chlorine gases form an explosive mixture, it is important to keep them separated. All three products are useful individually and they can also be combined together to make further products. Sodium hydroxide and chlorine combine to form sodium hypochlorite solution which is widely used in the home as domestic bleach. A stronger solution of sodium hypochlorite is used as a dairy and industrial disinfectant.

Under different reaction conditions, sodium hydroxide and chlorine will react to form sodium chlorate. This is produced as white crystals which can be highly explosive or inflammable if mixed with organic matter. Solutions of sodium chlorate are widely used as a herbicide.

When chlorine gas is burned in hydrogen, the two gases react to form hydrogen chloride. The hydrogen chloride dissolves in water to form hydrochloric acid. Hydrochloric acid made in this way is very pure, and can be used safely in the food and pharmaceutical industries.

Salt is a chemical compound with a number of interesting properties:

• Crystals or white crystalline powder.
• Transparent and colourless in crystalline form – rather like ice.
• Crystallises in the isometric system, usually in the form of cubes.
• Soluble in water (35.6g/100g at 0°C and 39.2g/100g at 100°).
• Slightly soluble in alcohol, but insoluble in concentrated hydrochloric acid.
• Melts at 801°C and begins to vaporize at temperatures just slightly above this boiling point 1,413°C.
• Hardness of 2.5 on the MOH scale of hardness.
• Specific gravity of 2.165.
• Non-combustible – low toxicity.
• Hygroscopic – absorbs moisture from damp atmospheres above 75 per cent relative humidity – below this, it will dry out.

In its natural form, salt often includes traces of magnesium chloride, magnesium sulphate, magnesium bromide, and others. These impurities can tint the otherwise transparent crystals, yellow, red, blue or purple.

The following are the different kinds of salt :

Normal salt

Normal salts are electrically neutral. They are formed when acids and bases neutralize, and these salts don’t have replaceable hydrogen or hydroxyl in their formula. Metallic ions replace the hydrogen ions completely.  For e.g. NaCl, KNO₃, CuSO₄ etc.

Basic salt

Salt formed due to partial replacement of hydroxy radicals of a diacidic base or a triacidic base with an acid radical. This kind of acid consists of hydroxyl, metallic cation and anion of an acid.  For e.g. basic Zinc chloride, basic magnesium chloride, ZnOHCL etc.

Acidic salt

If a polybasic acid is neutralized partly by a base, the salt formed is acidic. In other words, such salt is produced by the replacement of only a part of the acidic hydrogen of the polybasic acid by a metal.  For e.g. NaHSO₄,  NaHS, NaHCO₃ etc.

Double salt

Double salts have more than one cation or anion. They’re a crystalline salt having the composition of a mixture of two simple salts but with a different crystal structure from either. For e.g. bromlite, potassium sodium tartrate, aluminium sulfacetate etc.

Mixed salt

A mixed salt is a salt made from more than one base or acid.  For e.g. sodium potassium sulphate, bleaching powder etc.

Complex salt

Salt formed due to combining a saturated solution of simple salts followed by crystallization of the solution similar to double salts. For e.g. Sodium silver cyanide, potassium mercuric iodide etc.

• Salt is made up of Sodium and Chlorine.
• Salt has negatively charged ions (OH-) and positively charged ions (H+).
• Due to their oppositely charged ions, the ions are attracted towards each other with an electrostatic force of attraction which is called an ionic bond.
• An equal number of opposite charges makes the ionic compounds neutral with no charge.
• Salt water is a good conductor of electricity.
• Salts are ionic in nature due to the presence of ions.
• They are brittle, hard and crystalline solids.
• Salt is white, odorless and it has a salty taste.
• All potassium (K), ammonium (NH₄+) and sodium (Na) salts are soluble in water (H₂O).
• Nitrites, nitrates, and bicarbonates can be dissolved in water.
• All metallic oxides, metallic carbonates, hydroxides, phosphates, and sulphides are insoluble in water.

Salt is an ionic compound that results from the neutralization reaction of acids and bases. Salts are constituted of positively charged ions, known as cations and negatively charged ions, known as anions, which can either be organic or inorganic in nature. These ions are present in a relative amount, thus rendering the nature of the salt neutral.

The formation of salt can be seen from the chemical reactions shown in the equations below.

Hydrolysis of salt refers to the reaction of salt with water. It is the reverse of a neutralization reaction. In this reaction, when salt undergoes reaction with water, the constituent acid and base are formed as products. In hydrolysis, the salt dissociates to form ions, completely or partially depending upon the solubility product of that salt.

The compound’s sodium chloride has very different properties from the elements sodium and chlorine.

• Saltwater contains ions and is a fairly good conductor of electricity.
• This electrostatic force of attraction holds the ions together and a chemical bond is said to form between them.

1. Acidic salt – The salt formed by partial neutralization of a diprotic or a polyprotic acid is known as an acidic salt. These salts have ionizable H⁺ ion along with another cation. Mostly the ionizable H⁺ is a part of the anion. Some acid salts are used in baking.

For eg:- NaHSO_4­, KH₂PO₄ etc.

H₂SO₄  + NaOH →→  NaHSO₄  + H₂O

2. Basic or Alkali Salt – The salt formed by the partial neutralization of a strong base by a weak acid is known as a basic salt. They hydrolyze to form a basic solution. It is because when hydrolysis of basic salt takes place, the conjugate base of the weak acid is formed in the solution.

For eg:- White lead (2PbCO₃·Pb(OH)₂).

3. Double salt – The salts that contain more than one cation or anion are known as double salt. They are obtained by the combination of two different salts crystallized in the same ionic lattice.

For eg:- Potassium sodium tartrate (KNaC₄H₄O₆.4H₂O) also known as Rochelle salt.

4. Mixed Salts – The salt that consists of a fixed proportion of two salts, often sharing either a common cation or common anion is known as mixed salt.

For e.g. :- CaOCl₂

Salt is an ionic compound that contains a cation (base) and an anion (acid).

It is present in large quantities in seawater, where it is the main mineral constituent. Salt is essential for animal life and saltiness is one of the basic human tastes. Salt is an ionic compound that has a cation other than H⁺ and an anion other than OH^– and is obtained along with water in the neutralization reaction between acids and bases.

Eg:- NaCl, CuCl₂ etc.

Acid + Base →→ Salt + water

Sodium chloride is one of the best-known salt. One salt is known to almost everyone because of its widespread use in every day.