Group 7 Flashcards
What are the physical states of the halogens?
Fluorine: Yellow gas (g)
Chlorine: yellow- green gas (g)
Bromine: brown liquid ( l)
Iodine: grey-black solid (s)
Astatine: black solid (s)
Structure of group 7
Simple covalent molecule.
Covalent bonds between atoms
Induced dipole dipole forces between molecules
Exist as diatomic molecules.
Whats the trend in boiling point down group 7?
Bp increases down as theres more electrons in molecule so stronger induced dipole dipole forces between the molecules which takes more energy to overcome . (Induced dipole dipole forces are because group 7 exist as non polar molecules.)
Whats the reactivity of halogens as oxidising agents as you go down group?
All halogens oxidising agents with fluorine as most powerful as it attracts electrons most easily.
Less reactive ( oxidising power decreases) as go down because:
- outer electron gets further from nucleus
- shielding increases
- outer shell experience less nuclear attraction
- become harder to attract electron.
What is displacement ?
Reaction in which more reactive element displaces less reactive element in a from an aqueous solution of its halide ions.
What are the colours of displaced halogens in organic solvent and water?
In water In organic solvent
Cl2 - pale green Pale-green
Br2- orange. Orange
I2- Brown. Purple
What is the ionic equation and colour when chlorine is added to solution of potassium bromide?
Cl2 + 2Br- —> 2Cl- + Br2
Solution becomes yellow-orange as bromide is released. Reaction shows chlorine is better oxidising agents than bromine as chlorine displaces bromine.
What si the definition for disproportionation?
A reaction in which the same element is both oxidised and reduced.
What happens when chlorine disproportionated in aqueous sodium hydroxide to make bleach?
When chlorine reacted with aqueous sodium hydroxide disproportionates form solution containing chlorate and chloride ions. (Conditions: cold , dilute sodium hydroxide)
Cl2 (g) + 2NaOH (aq) —> NaCl (aq) +NaClO (aq) + H2O (l)
How does chlorine disproportionated in water?
Disproportionation occurs to form HCl and chloric acid.
Cl2 (g) + H2O (l) —> HCl (aq) + HOCl (aq)
Advantages / disadvantages of adding chlorine to drinking water.
Adv - destroys bacteria to make water safe to drink.
Dis- can be toxic , chlorine can react with organic compounds in water to form chlorinated hydrocarbons.
How do you test for halide ions in an aqueous solution? And what are the ionic equations for it?
Add silver nitrate solution then dilute or concentrated ammonia solution.
Ag+ (aq) + Cl- (aq) —> AgCl (s)
Ag+ (aq) + Br- (aq) —> AgBr (s)
Ag+ (aq) + I- (aq) —> AgI (s)
