Question

Give a brief account of the oxoacids of selenium.

Answer 1

1. Selenium forms oxoacids similar to sulphur, mainly selenous acid (H₂SeO₃) and selenic acid (H₂SeO₄).
2. Selenous acid (H₂SeO₃) is formed by oxidation of selenium and contains selenium in +4 oxidation state.
3. Selenic acid (H₂SeO₄) contains selenium in +6 oxidation state and is a stronger acid than selenous acid.
4. The stability and acid strength of selenium oxoacids are less than those of corresponding sulphur oxoacids.
5. Selenium trioxide (SeO₃) forms cyclic tetrameric structures in the solid state.
6. Selenium oxoacids show decreasing stability going down group 16 from sulphur to tellurium.
7. These oxoacids react as typical acids and have corresponding salts called selenites and selenates.