Sulfate, Sulfite and Sulfide

What is Sulfate?

The sulfate ion is a chemical compound consisting of one sulfur atom and four oxygen atoms surrounding it, forming a tetrahedral arrangement. It is a polyatomic anion having the empirical formula is SO₄^2-. The oxidation number of the sulfur atom is +6, and the oxygen atom is -2. Overall, there is a negative charge of 2 on the sulfate. The compounds having the sulfate ion are referred to as sulfate. Sulfates are commonly used in our everyday life. They are the salts of sulfuric acid. They are also the conjugate base of the bisulfate ion.

Preparation of Sulfate

Following methods are preferred for the preparation of sulfates:

• By the dissolution of any metal in the sulfuric acid
• When the metal oxide or hydroxide reacts with the sulfuric acid, sulfate ions are formed
• Oxidation of metal sulfides or sulfites

Properties of Sulfate

• Generally, sulfate ions are highly soluble in water, except calcium sulfate, strontium sulfate, and barium sulfate. These sulfates are poorly soluble in water
• Sulfate ions form a white residue.\The sulfate ion also acts as a ligand, binding the oxygen atoms together

Uses of Sulfate

• Sulfuric acid containing sulfate ions is used in lead-acid batteries
• Gypsum, the hydrated form of copper sulfate, is used to produce plaster
• Copper sulfate is used as galvanic cells as electrolytes
• Magnesium sulfates are used in therapeutic baths

What is Sulfite?

Sulfite ions consist of one sulfur atom with three oxygen atoms and a lone pair of electrons. As a whole, it possesses a -2 charge.  The shape of the sulfite ion is trigonal pyramidal. It has three equivalent resonance structures. The compounds that contain sulfite ions are known as sulfite. Sulfites are naturally found in our food and body. They are the conjugate base of the bisulfite ion.

Preparation of Sulfite

Sulfite ions are commonly prepared by dissolving carbon dioxide in water. This mixture leads to the formation of bisulfite. As we all know, sulfite is a conjugate base of bisulfite. They exist in equilibrium in an aqueous solution.

Properties of Sulfite

• Mainly sulfite salts are white
• They are soluble in water
• The salts formed by the sulfite ions are stable

Uses of Sulfite

• Sulfites are used as food preservatives
• Also used as dried agents
• Used to produce food colour

What is Sulfide?

Sulfide ions are the chemical compounds with the empirical formula S^2-. Therefore, the compounds that contain sulfite ions are known as sulfite. Sulfides are found as naturally occurring minerals in nature.

Preparation of Sulfides

The following reactions result in the formation of sulfides.

• By the direct combination of metals with sulfur
• By the reduction of sulfate
• By the precipitation of insoluble sulfide

Properties of Sulfide

• Solutions of sulfide salts are corrosive
• When reacted with an acid, the sulfide salts get converted into hydrogen sulfide gas
• Sulfides are not toxic
• The sulfide ion does not exist in the alkaline solution of Na₂S
• Organic sulfides are highly inflammable

Uses of Sulfides

• Rare earth sulfides are used in a thermoelectric device
• Metal sulfides are used as cathode in lithium-ion batteries

Difference between Sulfate, Sulfite, and Sulfide

Sulfate	Sulfite	Sulfide
The compounds containing the sulfate ions are known as sulfates	The compounds containing the sulfite ions are known as sulfites	The compounds containing the sulfide ions are known as sulfides
The empirical formula of sulfate ion is SO42-	The empirical formula of sulfite ion is SO32-	The empirical formula of sulfide ion is S2-
The oxidation number of sulfur in sulfate is +6	The oxidation number of sulfur in sulfite is +4	The oxidation number of sulfur in sulfide is -2
Sulfate ions  consist of four oxygen atoms	Sulfite ions consist of three oxygen atoms	Sulfide ions consist of no oxygen atoms

Conclusion

The confusion between sulfate, sulfite, and sulfide has been resolved. Firstly, these topics have been discussed in detail, and then the key differences between the three have been listed in tabular form. This will enable the user to clear all his doubts. Moreover, one will be able to know in detail about these topics.