The sulphate or sulfate ion is a polyatomic anion whose empirical formula is given by SO42-. The spelling of Sulfate is suggested by the IUPAC but british english uses Sulphate. Acid derivatives, salts and sulphate peroxides are used widely in industries and also exist widely in daily life.
The anion contains a central sulphur atom neighboured by four atoms of oxygen in a tetrahedral positioning wherein the arrangement is similar to methane. An atom of sulfur is present in +6 oxidation state and four oxygen atoms are in -2 state. Hence the sulphate ion holds a -2 charge being a conjugate base of bisulfate ion, HSO–4 (hydrogen sulfate) as a conjugate base of Sulfuric acid, H2SO4. Organic esters of sulfate like dimethyl sulfate come under esters of sulfuric acid and covalent compounds. The tetrahedral geometry of sulphate ion based on VSEPR theory.
These are the most opted methods to prepare metal sulfates.
- Oxidation of metal sulphites and sulphides.
- Treating metal hydroxide, metal oxide and metal with sulfuric acid.
Properties of Sulphate
Various instances of ionic sulfates are well known which are soluble in water. Exceptions involve strontium sulfate, calcium sulfate, barium sulfate and lead(II) sulphate being weak soluble. When one adds barium chloride solution to a solution consisting of sulfate ions, barium sulfate appears in the form of white precipitate that shows the presence of sulfate anions.
The sulfate ion acts as a ligand connecting either by two oxygens or by single oxygen as a bridge. For example the complex of a neutral metal PtSO4 wherein the sulfate ion acts as a bidentate ligand. The metal-oxygen bonds consist of a particular covalent character in complexes of sulphate.
- Sulfates hold wide applications in industries whose major compounds involve:
- Copper sulfate is the most common algaecide.
- Magnesium sulfate is used in therapeutic baths.
- Gypsum is a natural form of hydrated calcium sulfate used in making of plasters.