The Halogens
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What happens down the halogen group in terms of boiling point?
It increases
Explain the trend in boiling point down the halogen group
Id-Id or London forces increase so more energy is needed to overcome them
What happens down the halogen group in terms of reactivity with halide ions?
Decreases
Explain the trend in reactivity down the halogen group with halide ions
The added electron is further from the nucleus and it shielded by more electrons in inner shells so the electrostatic attraction decreases and so reactivity decreases
What are displacement reactions in terms of halogens?
Reactions in which a more reactive halogen will oxidise and displace a less reactive halogen from its salt
What can halogen solutions be added to, to produce displacement reactions?
NaCl NaBr NaI
What is the colour of chlorine in water?
Pale green
What is the colour of bromine in water?
Orange
What is the colour of iodine in water?
Brown
What is the colour of chlorine in cyclohexane?
Pale-green
What is the colour of bromine in cyclohexane?
Orange
What is the colour of idoine in cyclohexane?
Purple
What happens to show that a redox reaction has taken place with halogens reacting with halide ions?
A colour change
What is usually also added to the solution of halogen and sodium halide?
Usually shaken with cyclohexane to distinguish between bromine and iodine
Which halogen in the most reactive?
Chlorine
What is the colour change of halogens determined by?
The halogen in the solution - the most reactive halogen oxides the halide ions and so becomes the halide ions so the colour is determined by the halogen
The equation of chlorine and water in water treatment
Cl2 + H2O ———-> HClO + HCl
Equation of chlorine and sodium hydroxide and what it forms (specific ion)
Cl2 + 2NaOH ----------> NaCl + NaClO + H2O Forms bleach (ClO-)
What conditions are needed for when chlorine makes bleach
Reacts with cold, dilute aqueous NaOH
Name 2 negatives for the chlorination of water
Cl’s toxicity means care has to be taken Can react with organic matter to form chlorinated hydrocarbons which may be carcinogenic