Question

What is the name of \[SO_{4}^{2-}\] ion?
a.) Persulfate
b.) Sulfate
c.) Sulfite
d.) Hyposulfite
e.) Sulfide

Answer 1

Hint: -Ate is the suffix used for the ions where the central atom is in its highest oxidation state and per suffix is used when oxygen-oxygen bond is present in the ion. Also we must remember the number of electrons in sulfur atom’s valence shells are 6, so the highest oxidation number it can show is 6.

Complete step by step answer:
$SO_{4}^{2-}\to $ Here one sulfur atom is attached to 4 oxygen atoms. So it’s possible structure can be as shown below:

- In this structure two oxygen atoms have formed multiple bonds with sulfur and two oxygen atoms have formed a single bond. As we know oxygen atoms are more electronegative than sulfur and because of that sulfur will bear +1 positive charge for each bond it has formed with oxygen.
Total bonds formed with oxygen over here = 6
Total formal positive charge on Sulfur = +6
Oxidation number of sulfur= +6
As oxidation number of sulfur is its highest possible oxidation number and no oxygen-oxygen bond is present over here so the name of this ion will be Sulfate.
Persulfate ion: ${{S}_{2}}O_{8}^{2-}$
Sulfite ion: $SO_{3}^{2-}$
Hyposulfite ion: ${{S}_{2}}O_{3}^{2-}$
Sulfide ion: ${{S}^{2-}}$

Additional Information : Sulfates occur as microscopic particles (aerosols) resulting from fossil and biomass combustion. They increase the acidity of the atmosphere and form acid rain.

Note: Sulfate ion present in general along with phosphate for qualitative analysis of ions. Confirmatory tests of sulfate ion are as follows:
a.) Aqueous solution or sodium carbonate extract of the salt acidified with acetic acid in addition to barium chloride gives a white precipitate of barium sulfate insoluble in conc. $HCl$ or conc. $HN{{O}_{3}}$ .
b.) Sulfate ions give white precipitate of lead sulphate when aqueous solution or sodium carbonate extract neutralised with acetic acid is treated with lead acetate solution.