Study of Compounds — Gas Evolution & Confirmatory Tests

An open bench spanning all four Study of Compounds gases. Students drag reagents into the flask — conc. H₂SO₄, conc. HNO₃, conc. and dil. HCl, copper turnings, sodium chloride, manganese dioxide, sodium nitrate, ammonia solution — heat where the reaction needs it, and confirm the gas with a probe: acidified K₂Cr₂O₇ paper turning orange→green for SO₂, an ammonia-wetted rod giving white fumes for HCl, a conc.-HCl rod doing the same for NH₃, plus litmus, methyl orange, phenolphthalein and Nessler's reagent. A second track of qualitative tests runs alongside — AgNO₃ + HCl giving curdy white AgCl that redissolves in excess ammonia, BaCl₂ + H₂SO₄ giving white BaSO₄, and CuSO₄ + NH₄OH stepping from a pale-blue hydroxide precipitate to the deep-blue tetraamminecopper(II) complex on excess ammonia. Sixteen guided tests across all four groups (three each for sulphuric, hydrochloric and nitric acid, four for ammonia) walk the standard sequences step by step, and every reagent pairing is answered, so a wrong guess is a result rather than a dead end.