HALOGENS Flashcards
Describe fluorine (F2)
Pale yellow
Gas
Highly reactive
Describe chlorine (Cl2)
Greenish
Gas
Reactive
Poisonous in high concentrations
Describe bromine (Br2)
Red
Liquid
Gives off brown/orange poisonous fumes
Describe iodine (I2)
Shiny grey
Solid
Sublimes to purple gas
Describe the trend in melting point and boiling point in halogens
Increase down the group
As the molecules become larger they have more electrons
Larger Van Der Waals forces between molecules
More energy required to break the forces
Describe the trend in electronegativity of halogens
Decreases down the group
Increased atomic radii
Increased number of shells
Nucleus less able to attract bonding pairs of electrons
Describe the trend of halogens as oxidising agents
Decreases down the group
Strong halogen oxidising agents displace halogens with lower oxidising agents
From one of its compounds
Describe the reaction between aqueous chlorine and aqueous potassium chloride
Pale green solution
No reaction
Describe the reaction between aqueous chlorine and aqueous potassium bromide
Yellow solution
Cl displaces Br
Describe the reaction between aqueous chlorine and aqueous potassium iodide
brown solution
Cl displaces I
Describe the reaction between aqueous bromine and aqueous potassium chloride
Yellow solution
No reaction
Describe the reaction between aqueous bromine and aqueous potassium bromide
Yellow solution
No reaction
Describe the reaction between aqueous bromine and aqueous potassium iodide
Brown solution
Br displaces I
Describe the reaction between aqueous iodine and aqueous potassium chloride
Brown solution
No reaction
Describe the reaction between aqueous iodine and aqueous potassium bromide
Brown solution
No reaction
Describe the reaction between aqueous iodine and aqueous potassium iodide
Brown solution
No reaction
Outline the reactions of halide ions with silver nitrate
Fluoride = no precipitate
Chloride = white precipitate
Bromide = Cream precipitate
Iodide = Pale yellow precipitate
Describe the role of nitric acid in the reaction of halide ions with silver nitrate
Halide ion is dissolved in nitric acid
To react with any carbonates present
And prevent formation of Ag2CO3
Which would mask the desired observations
Describe the reactions of silver halide precipitates and ammonia
AgCl = dissolves in dilute ammonia but not concentrated
AgBr = dissolves in dilute and concentrated ammonia
AgI = does not react with ammonia
Describe the trend of halides as reducing agents
Increases down the group
Larger ion
Easier to donate outer electrons
Weaker attraction to nucleus
Outline the reaction of fluoride salts with concentrated sulphuric acid
Acid-base reaction
NaF(s) + H2SO4 (l) > NaHSO4(s) + HF(g)
White steamy fumes
Outline the reaction of chloride salts with concentrated sulphuric acid
Acid-base reaction
NaCl(s) + H2SO4 (l) > NaHSO4(s) + HCl(g)
White steamy fumes
Outline the reaction of bromide salts with concentrated sulphuric acid
Acid-base reaction
NaBr(s) + H2SO4 (l) > NaHSO4(s) + HBr(g)
White steamy fumes
Redox reaction
2HBr + H2SO4 > Br2(g) + SO2(g) + 2H2O(l)
Red bromine fumes
Colourless acidic gas
What are the two half equations or the redox step in bromine salts reacting with concentrated sulphuric acid
OX: 2Br- > Br2 + 2e-
RED: H2SO4 + 2H+ + 2e- > SO2 + 2H2O
Outline the reactions of iodide salts with concentrated sulphuric acid
NaI(s) + H2SO4 > NaHSO4(S) + HI(g)
2HI + H2SO4 > I2(s) + SO2(g) + 2H2O(l)
6HI + H2SO4 > 3I2(s) + S(s) + 4H2O(l)
8HI + H2SO4 > 4I2(s) + H2S(g) + 4H2O(l)
Outline the observations of iodide salts with concentrated sulphuric acid
White steamy fumes
Black solid
Purple fumes
Colourless acidic gas
Yellow solid
Bad egg smell
Define disproportionation
A reaction where an element simultaneously oxidises and reduces
Reaction of chlorine with water
Cl2(aq) + H2O(l)> HClO(aq) + HCl(aq)
Reaction of chlorine with water in the presence of sunlight
2Cl2 + 2H2O > 4H+ + 4Cl- + O2
What is the use of a disproportionation reaction between chlorine and water
Treatment to kill bacteria
Drinking water
Swimming pools
Health outweighs toxic effects
Reaction of chlorine with old dilute NaOH(aq)
Fades to colourless
Cl2(aq) + 2NaOH(aq) > NaCl(aq) + BaClO(aq) + H2O
What is NaCl and NaClO used for
Bleach
To disinfect
And kill bacteria
Name the chlorates and sulphates
NaClO sodium chlorate(I)
NaClO3 sodium chlorate (V)
K2SO4 potassium sulphate (VI)
K2SO3 potassium sulphate (IV)