Group 7 Physical and Chemical properties Flashcards
Fluorine state and colour at room temp
Gas
Pale yellow
Chlorine state and colour at room temp
Gas
Green
Bromine state and colour at room temp
liquid
Brown with orange vapour
Iodine state and colour at room temp
Solid
Black/grey with purple vapour
Chlorine colour in solution
Colourless
Bromine colour in solution
Orange/brown
Iodine colour in solution
Dark brown/black
Trend in boiling point in group 7
Boiling point increases down the group
Halogen molecules increase in size and have more electrons
Stronger van der waals forces
Require more energy to break the intermolecular forces
Trend in electronegativity for halogens
Halogens form more electron shields between bonding pair of electrons and positive nucleus
Electrostatic attraction decreases
So electronegativity decreases
Order of oxidisation of halogens
F2
Cl2
Br2
I2
Equation for chlorine sterilising water
No UV light
Cl2 + H2O <-> HCl + HClO
Disproportionate reaction
Reduced and oxidised in same reaction
Why is the ClO ion important for sterilising
ClO ion oxidises the cell membrane of microbes, killing them
Reaction of Cl2 with cold aqueous NaOH
Cl2 + 2NaOH —> NaCl + NaClO + H2O
Why is Cl2 used to sterilise despite toxicity
Benefits outweigh risks
Concentration of chlorine is low
Chlorine and water reaction
IN UV LIGHT
2Cl2 + 2H2O —> 4HCl + O2
identify metal halide of Fluoride + colour/observation and solubility
Ag+(aq) + F-(aq) —> AgF (aq)
No observation, silver fluoride soluble in water
No precipitate formed
Identify metal halide of Chlorine + colour and solubility
Ag+ + Cl- —> AgCl (s)
White precipitate
Soluble in NH3
Identify metal halide of Bromine + colour and solubility
Ag+ + Br- —> AgBr (s)
Cream precipitate
Soluble in excess NH3
Identify metal halide of Iodine + colour and solubility
Ag+ + I- —> AgI (s)
Yellow precipitate
Insoluble in NH3
What are the spectator ions when identifying metal halides with silver ion
Na+
NO3-
Why should the silver nitrate solution be acidified when testing for metal halides
Prevent formation of Ag2CO3 which can form white precipitate, confusing the results
What are the disadvantages of using chlorine as a sterilising agent
Some people are allergic
Wasteful - most potable water isn’t used for drinking
