Question

Oxidation number of S in H₂SO₅

Answer 1

Oxidation number of S in H₂SO₅

( Permonosulphuric acid or Caro’s acid)

By usual method; H₂SO₅

2 x 1 + a + 5 x (-2) = 0 or a = + 8

But this cannot be true as maximum oxidation number for S cannot exceed + 6, Since S has only 6 electrons in its valence shell. This exceptional value is due to the fact that two oxygen atoms in H₂SO₅ shows peroxide linkage as shown below,

Therefore the evaluation of O.N. of sulphur here should be made as follows,

2 x (+1) + a + 3 x (-2) + 2 x (-1)

(for H) (for S) (for O) (for O-O)

or 2 + a - 6 - 2 = 0 or a = + 6