Halogens 6.5 6.5 Reaction with H2SO4 & H3PO4
Solid halide salts react with sulphuric acid as both an oxidising agent and an acid. Phosphoric acid however acts only as an acid. Results are below.
Product Tests↓Salt→KClKBrKI
Add NH3 to test for HHal gas Proton donated by Acid. KCl + H2SO4 → KHSO4 + HCl
Is a Halogen vapour seen? NO - the acid isn't reduced. YES - Oxidation in 2Hal- → Hal2 + 2e-. Bromine: Brown gas & Iodine: Purple.
Is SO2 produced? (KDichromate → green) NO - the acid isn't reduced. YES - Acid is reduced by halide ions.
H2SO4 + 2e- + 2H+ → SO2 + 2H2O
Is H2S produced?
(Pb ethanoate → black)		 NO - the acid isn't reduced. NO - the acid isn't reduced YES H2SO4 + 8e- + 8H+ → H2S + 4H2O


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