Sulphate

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What is Sulphate?

Sulphate also spelled as Sulfate is a chemical compound that is composed of sulphur and oxygen atoms. It is one of the most widely available chemical compounds accessible as naturally occurring minerals on earth. It is mostly found in the environment as a result of atmospheric and terrestrial processes. The major contributors of sulphate are sulphide containing rocks and minerals, sulphur released from the erosion of evaporite deposits, and even volcanoes. Sulphate is a derivative of salts with a variety of elements including potassium, sodium, calcium, magnesium, and barium.

Sulphate Formula: SO42-


IUPAC Name

Sulfate

Chemical Formula

SO42-

Molar Mass

96.06 g·mol-1

Boiling Point

623.89 °C

Melting Point

270.47 °C


Sulphate Structure [SO42-]

Let us understand the chemical bonding and molecular structure of sulphate. The sulphate ion is composed of sulphur and oxygen atoms. Here, sulphur is the central atom and it is surrounded by four oxygen atoms that are located at equal distances in the plane. As for the bonding, 2 of the oxygen atoms form S=O bonds, and the other two form S-O- bonds. The oxygen atoms are responsible for the negative charge (-2) of the anion because they are in -2 state.


If we look at the structure or the shape of the molecule, it has a tetrahedral geometry which is further based on the VSEPR theory. Sulphate ion has a star-shaped geometry. It is represented as:


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The atoms are placed at 109.5° angle. To determine the structure students can learn to draw the Lewis structure of sulphate and also know about the formal charges and the total number of valence electrons needed for sulphate.


Properties of Sulphate

The physical and chemical properties of sulphate ions are as given below.

Physical Properties of Sulphate

  • Ionic sulphates are easily soluble in water. There are some exceptions such as strontium sulphate, calcium sulphate, barium sulphate, and lead sulphate. These sulphates have less solubility.

  • Also, they form white precipitates during reactions.

Chemical Properties of Sulphates

  • A chemical property of sulphate is that it can easily combine with metals. To expand it further, the oxygen atoms in sulphate ion act as ligands (arms) and they attract the metal to form a bridge or connection. This interlink of a chemical compound bonding with metal is called a chelate.

  • The sulphate ion acts as a ligand connected either by two oxygens or single oxygen as a bridge. Sulphate has so many electrons, it can use any pair of electrons to connect with a metal.

For example, let us take a neutral metal PSO4 wherein the sulphate ion acts as a bidentate ligand. The metal and oxygen bonds consist of a particular covalent character in sulphate complexes.

  • The sulphate ion is a conjugate base of bisulfate ion, HSO-4 (hydrogen sulphate), and a conjugate base of sulphuric acid, H2SO4. The organic esters of sulphate like dimethyl sulphate come under esters of sulphuric acid and covalent compounds.

Preparation of Sulphate

There are usually two methods to prepare sulfates.

  • Oxidation of metal sulphites and sulphides. However, the formation of sulphate as the final state of oxidation may be determined by consecutive reactions that are critically dependent on other factors such as the catalyst, etc.

  • Sulphates can be prepared by treating metal hydroxide, metal oxide, and pure metal with sulfuric acid. Some of the examples are:

Ba(ClO3)2 + H2SO4 → 2 HClO3 + BaSO4

Zn + H2SO4 → ZnSO4 + H2

Cu(OH)2 + H2SO4 → CuSO4 + 2 H2O

During the preparation of sulphate remember that sulfuric acid should be deprotonated twice, if it occurs only once, then hydrogen sulphate ion is made.


Sulphate Examples

Here are some examples of sulphates.

  • Magnesium Sulphate

  • Copper Sulphate

  • Gypsum

  • Sodium Sulphate

  • Iron (II) Sulphate

  • Hydrogen Sulphate

  • Calcium Sulphate

  • Lead Sulphate

  • Sodium Lauryl Sulphate

Sulphate Uses

Sulphates are easily available in nature and also easily synthesized in industries. Therefore, this chemical compound has applications in a wide variety of products. Some of the sulphate uses are listed below.

  • Magnesium sulphate is used in therapeutic baths.

  • Sulphate minerals are used in the making of metal salts.

  • Copper sulphate is the most common algaecide.

  • They are used in detergents, emulsifiers, and foaming agents.

  • Gypsum is a natural form of hydrated calcium sulphate used in the making of plasters.

  • Sulphate compounds are also found in cosmetic products such as toothpaste, body sprays, lotions, make-up, soaps, shampoos, etc.

  • They are used in construction.

  • They are powerful surfactants and are found in most products that are used to remove grease from heavy machinery.

  • Copper sulphate is used in the electricity domain and barium sulphate is used in water treatment.

  • Sulphates are added to cleaning products to make them more effective cleaners.

Sulphate Effects and Hazards

Some of the popular hazards and health effects are:

  • Naturally, sulphates can occur as microscopic particles called aerosols which is a result of fossil fuel and biomass combustion. This can lead to an increase in the acidity of the atmosphere and the formation of acid rain.

  • As for the effects on humans, it can cause dryness of skin, ruin hair cuticle, and they usually leave the hair with a negative charge.