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Group 7 (Reactions of halogens with cold NaOH (Its a disproportionation…
Group 7
Reactions of halogens with cold NaOH
Its a disproportionation reaction as the chlorine is oxidised and reduced
Uses for reaction- bleach to kill bacteria
Cl2 + NaOH -> NaCl + NaClO + H2O
Same reaction occurs with bromine and iodine
Observation- fades to colourless
Reactions of hydrogen halides with water
HX + H2O -> H+ + X-
During the reaction the single covalent bond breaks heterolytically so both electrons move to the hydrogen ion (becomes H+)
Hydrogen halides are covalent molecules which dissolve in water to give aqueous solutions of hydrogen ions (H+) and Halide ions (X-)
Solution formed is acidic
Reactions of hydrogen halides with ammonia
General equation Hydrogen halide + ammonia -> Ammonium Halide
2 colourless gases make white misty fumes
Example- Hydrogen chloride + ammonia -> Ammonium Chloride
Reactions of halogen with hot NaOH
Disproportionation reaction- Iodine is oxidised and reduced
Ionic equation - 3I2 + 6OH- -> 5I- + IO3- + 3H2O
3I2 + 6NaOH -> 5NaI + NaIO3 + 3H2O