Group 7 - the halogens -2
- Created by: Shannon
- Created on: 09-05-14 11:18
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- Group 7
- Physical properties
- Flourine
- Pale yellow gas
- Chlorine
- Green gas
- Bromine
- Red/brown liquid
- Iodine
- Silver solid
- Appearance in water
- Flourine
- N/A
- Chlorine
- Virtually colourless
- Bromine
- Yellow/orange
- Iodine
- Brown
- Flourine
- Appearance in hydrocarbon solvents: hexane
- Flourine
- N/A
- Chlorine
- Virtually colourless
- Bromine
- Orange/red
- Iodine
- Pink/violet
- Flourine
- Flourine
- Oxidation reactions
- With non-metals
- E.g chlorine reacts with sulfur to form sulfur(I) chloride
- With metals
- Fluorine & chlorine react with hot iron to form iron(III) halides
- Bromine is weaker oxidising agent and so there is a mixture of iron(II) and iron(III) bromide
- No iron(III) ions form with iodine
- With non-metals
- Reactivity
- Halogens react by gaining an electron, so they oxidise another species
- Down the group they become less oxidising
- Their reducing power increases down the group
- Down the group they become less oxidising
- Halogens react by gaining an electron, so they oxidise another species
- Disproportionation reactions
- Halogens react with hot and cold alkali
- The halogen is simultaneously oxidised and reduced
- Halogens react with hot and cold alkali
- Reactions with conc. sulfuric acid
- Potassium halides react with conc. sulfuric acid to give acid and a hydrogen halide
- KF or KCl - HF or HCl gas given off
- HF and HCl aren't strong enough reducing agents to continue the reaction
- KBr - HBr gas produced in the first reaction
- HBr is a strong reducing agent and so reacts with sulfuric acid in a redox reaction
- SO2 produced
- HBr is a strong reducing agent and so reacts with sulfuric acid in a redox reaction
- KI - HI gas produced in first reaction
- HI reduces the sulfuric acid the strongest
- H2S produced
- HI reduces the sulfuric acid the strongest
- KF or KCl - HF or HCl gas given off
- Potassium halides react with conc. sulfuric acid to give acid and a hydrogen halide
- Testing for the presence of halides
- Addition of silver nitrate
- Flourine
- No ppt forms
- Chlorine
- White ppt
- Redissolves in dilute NH3
- White ppt
- Bromine
- Cream ppt
- Redissolves in conc NH3
- Cream ppt
- Iodine
- Pale yellow ppt
- Will not redissolve
- Pale yellow ppt
- Flourine
- Addition of silver nitrate
- Reactions of hydrogen halides with water and ammonia
- Ammonia
- Produces an ammonium halide
- Water
- Produces a strong acid
- Ammonia
- Iodine/Thiosulfate titration
- Iodine is a common oxidising agent, whilst thiosulfate is a common reducing agent
- Starch is used as an indicator
- Blue/black in the presence of iodine
- S2O32-
- Observed colour changes of solution: brown -> pale yellow, pale yellow -> blue/black, blue/black->colourless
- Physical properties
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