A-level chemistry

1. The Halide Salts. Aim: To identify and understand the general properties of the halide salts. To understand that halide ions are reducing agents and identify their reactions with concentrated sulphuric acid.

6. Reaction of Halide Salts with Conc. Sulphuric Acid. Acid + Halide salt can make Hydrogen halides – HCl, HBr, HI. NaCl + H 2 SO 4 HCl + NaHSO 4 These products can go on to react with the sulphuric acid – and reduce it. How would we prove that hydrogen halides are produced in the reaction? Hydrogen halides make dense white fumes when they react with conc ammonia solution. What is the equation for this type of reaction? NH 3 + HCl NH 4 Cl

7. Reaction of Hydrogen Halides with Conc Sulphuric acid. Possible products when hydrogen halides react with Conc sulphuric include sulphur dioxide, Hydrogen Sulphide and the Halogen itself. How do you test for Sulphur dioxide? Acidified potassium dichromate paper turns form orange to green if sulphur dioxide is present. (Reaction type?) How do you test for Hydrogen Sulphide? It smells of rotten eggs! How do you identify the halogens? Chlorine – Bleaches damp blue litmus paper. Bromine – Slowly as above + distinctive colour. Iodine – Distinctive colour

8. Reaction of Halides with Sulphuric Acid. KI. KBr KCl Inference Confirmatory test Observation with conc Sulphuric acid Halide

9. Reaction of Halides with Sulphuric Acid. HI, I2 & H2S & SO2 White smoke with ammonia – HI acidified potassium dichromate(VI) goes from orange to green – SO2 Steamy violet fumes in cold, more on warming (I2), bad egg smell (H2S) KI. HBr & Br2, & SO2 White smoke with ammonia HBr. acidified potassium dichromate(VI) goes from orange to green – SO 2 . Steamy fumes in cold, brown gas on warming (Br2) KBr HCl White smoke with ammonia - HCl, damp litmus paper turns red (not bleached) – no Cl2 Steamy fumes in cold, no apparent effect when heated KCl Inference Confirmatory test Observation with conc Sulphuric acid Halide

11. Reaction of KBr and Sulphuric Acid.