|
|
Revision:Chemistry Unit 1.7 - Group 7 (The Halogens)TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > Chemistry Unit 1.7 - Group 7 (The Halogens) A Level Chemistry Unit 1.7 - Group 7 (The Halogens).
Physical propertiesThe halogens are diatomic molecules They also have many common properties:
Chemical tests
Hydrogen halidesHydrogen halides are very soluble in water, for example hydrogen chloride gas dissolves readily in water.
HCl dissolves well in water because HCl is a polar molecule as is water and so the intermolecular forces are favourable. Hence the HCl and H2O molecules will have permanent dipole interactions to such an extent the HCl dissociates. Identification of the halidesReactions of halide salts with H2SO4Chloride salts
Bromide salts
Iodide salts
As it can be seen, as you descend the group the halide ions become more easily oxidised. In fact The chlorate(I) and chlorate(V) ionsThere are two oxo-anions of chlorine each with different oxidation numbers: The chlorate(I) ion – The chlorate(v) ion – DisproportionationThis occurs when a species is simultaneously oxidised and reduced. Chlorine undergoes this in an alkaline environment: The chlorate(I) ion also undergoes disproportionation but on heating: The halogens as oxidising agentsAs you descend group 7, the halogens become less effective as an oxidising agent. This property can be used in the extraction of bromine from seawater. If Chlorine gas is passed through seawater then the bromide ions are oxidised to bromine. Therefore Cl2 is a better oxidising agent than bromine. Comments |