Answer: +6 (one S-OH and one S-O-O-H group making it a peroxoacid).
- A +6 (one S-OH and one S-O-O-H group making it a peroxoacid)
- B +4, the oxidation state characteristic of sulfur in SO<sub>2</sub> instead
- C +8, an oxidation state not actually accessible to sulfur in any compound
- D +2, an unusually low oxidation state not seen in this peroxoacid
Correct answer: A. +6 (one S-OH and one S-O-O-H group making it a peroxoacid)
Explanation: H₂SO₅ is peroxomonosulphuric acid (also called Caro acid). The peroxy O-O linkage contributes -1 per O (not -2). 2(+1) + S + 4(-2) + 1(-1) = 0, giving S = +6. The S is +6 but one O is the peroxide type (-1).
Electron transfer in a redox reaction: zinc loses electrons (oxidised, acts as reducing agent) and copper(II) ions gain those same electrons (reduced, acts as oxidising agent).
Concept context
Master electron transfer in chemistry: assign oxidation states, balance half-reactions, identify oxidising and reducing agents, and connect redox to everyday reactions.