1. Properties of the halogens
Tuesday 11th January
The Halogens – Group 7
Properties of the halogens
This lesson we will…
Describe the physical properties of the Group 7 elements

2. Write half-equations for the following conversions:
Fe3+ to Fe2+ C2O42- to CO2 Fe3+ + e-  Fe2+ 2Fe3+ + 2e-  2Fe2+ C2O42-  2 CO2 + 2 e- 2Fe3+ + C2O42-  2Fe2+ + 2CO2
Fe3+ + e-  Fe2+
C2O42-  2 CO e-
Now combine the half-equations to produce a redox equation:
X 2

3. Group VII – The Halogens
Fluorine
Chlorine
Bromine
Iodine
Astatine Fl Fn F Cl Ch C Br Bn B Io In I As At An

4. Electron ConfigurationsCl Br I
{He} 2s2 2p5
{Ne} 3s2 3p5
{Ar} 4s2 3d10 4p5
{Kr} 5s2 4d10 5p5

5. You should have in your notes: 1
You should have in your notes: 1. the colours and states of the halogens at room temperature 2. the colours of the halogens dissolved in water 3. the colours of the halogens dissolved in a hydrocarbon solvent

6. Halogens in Hexane

7. Tests for halogens in solution
Chlorine
Add a drop of the solution to some damp blue litmus paper. If it turns red and then white, chlorine is present.
Bromine
Add some hexane solution. Observe a colour change to orange-brown.
Iodine
Add some hexane solution. A pink-purple layer will form above the solution if iodine is present.

8. What is the oxidation number of chlorine in these molecules?
Cl2
NaClO
NaCl +1 -1
NaClO3 +5

9. Chlorate Ions
ClO- This is called the chlorate (I) ion ClO3- This is called the chlorate (V) ion A roman numeral in brackets represents the oxidation number of an element.

10. Wednesday 12th January
Halogen Reactivity

11. Name each of these ions or molecules:
Cl-
BrO- I2
chloride
bromate (I)
iodine
ClO-
IO3-
Br -
chlorate (I)
iodate (V)
bromide

12. Molecules / Ions for Group 7
Halogens
Halide ions
Halate (I) ions
Halate (V) ions
chlorine
Cl2
chloride
Cl-
chlorate (I)
ClO-
chlorate (V)
ClO3-
bromine
Br2
bromide
Br -
bromate (I)
BrO-
bromate (V)
BrO3-
Iodine I2
iodide I-
iodate (I)
IO-
iodate (V)
IO3-
A roman numeral in brackets represents the oxidation number of an element.

13. Disproportionation = when one element is simultaneously oxidised and reduced in a reaction
When chlorine reacts with cold sodium hydroxide: Cl2 (g) + 2NaOH (aq) -> NaCl (aq) + NaClO (aq) + H2O (l) When the sodium hydroxide is hot, further disproportionation is observed: 3Cl2(g) + 6NaOH (aq) -> 5NaCl (aq) + NaClO3 (aq) + 3H2O(l) For bromine and iodine, the formation of the halate (V) ion is very rapid. Very cold temperatures are needed to isolate the halate (I) ion.

14. Summary of products with addition of sodium hydroxide
Addition of cold NaOH
Addition of hot NaOH
Cl2
NaCl, NaClO
NaCl, NaClO3
Br2
NaBr, NaBrO
NaBr, NaBrO3 I2
NaI, NaIO
NaI, NaIO3

15. Define the following in terms of electron transfer:
Reduction
The gain of electrons
Oxidation
The loss of electrons
Reducing agent
A species which donates electrons to something else
Oxidising agent
A species which removes electrons from something else

16. Halogen Redox Reactions
In order to determine oxidising ability, react each element with the metal halides of the other two.
If a redox reaction occurs:
Metal Halogen(B) Metal Halogen(A)
Halide(A) Halide(B)
We need to be able to test for the halogen produced.

17. Halogen Redox Reactions
Record your results in a table like this one:
Write word and symbol equations for the reactions which have taken place.
Cl2
Br2 I2
NaCl
NaBr
NaI

18. Tests for halogens Chlorine
Add a drop of the solution to some damp blue litmus paper. If it turns red and then white, chlorine is present.
Bromine
Add some hexane solution. Observe a colour change to orange-brown.
Iodine
Add some hexane solution. A pink-purple layer will form above the solution if iodine is present.

19. Halogens in Hexane

20. 2NaBr + Cl2 2NaCl + Br2 +1 -1 +1 -1 2NaI + Cl2 2NaCl + I2 +1 -1 +1 -1
Write the oxidation numbers of all of the elements in the reactions:
What is being oxidised?
What is being reduced?
What is the oxidising agent?
What is the reducing agent?
2NaBr Cl NaCl Br2 +1 -1 +1 -1
2NaI Cl NaCl I2 +1 -1 +1 -1
2NaI Br NaBr I2 +1 -1 +1 -1
Na+ can be classed as a spectator ion in these reactions, as it is not involved in the redox process.

21. Reaction of Metal Halides with Silver Nitrate
This lesson we will...
Carry out and describe the effect of silver nitrate on metal halides, and the effect of sunlight on the silver halides

22. Metal Halides with Silver Nitrate
This is an effective method of identifying the halide ion present in a compound.
We are going to look at NaCl, NaBr, NaI.

23. Method: for reactions of NaCl, NaBr, NaI
Put approx 1cm3 of metal halide solution into a test tube.
Add approx 1cm3 of silver nitrate solution.
Shake gently.
Note whether a precipitate is formed, and if so, note the colour.
If a precipitate forms, add dilute ammonia. Note whether the precipitate dissolves.
If the precipitate does not dissolve, add concentrated ammonia. Note whether or not it dissolves.
Carry out steps 1-3 again and then leave to stand by the window. Note down any observations.

24. Results Table Addition of AgNO3 Addition of dilute ammonia
Addition of conc ammonia
NaCl
NaBr
NaI

25. Trends in Halogen Reactivity
Tuesday 18th January
Trends in Halogen Reactivity

27. Redox reactions of the halogens
Oxidising ability increases up the group
Better at removing electrons from another species and becoming halide ions
Very good oxidising agents
Fluorine
Chlorine
Bromine
Iodine
Astatine
Less good oxidising agents

28. (iii) Why does this combination of sodium iodide and chlorine lead to a reaction, whereas a combination of sodium chloride and iodine doesn’t?

29. MgCl2 + F2 NaI + Br2 KBr + Cl2 CaCl2 + Br2 MgF2 + Cl2 2 2NaBr + I2 2
Which of these combinations will lead to a reaction? Complete a balanced equation for those that react:
MgCl2 + F2
NaI + Br2
KBr + Cl2
CaCl2 + Br2
MgF2 + Cl2 2
2NaBr + I2 2
2KCl + Br2
NO REACTION

30. Metal Halides with Silver Nitrate
This is an effective method of identifying the halide ion present in a compound.

31. The silver halides

32. Results Addition of AgNO3 Addition of dilute ammonia
Addition of conc ammonia
NaCl
White precipitate
Precipitate dissolves
NaBr
Cream precipitate
No change
NaI
Yellow precipitate

33. What was formed?
The precipitates formed when solutions of sodium halides are added to silver nitrate (AgNO3) are called silver halides:
AgCl silver chloride
AgBr silver bromide
AgI silver iodide
Write word and symbol equations for the formation of these precipitates.

34. Silver halides become less soluble down the group
Solubility in Ammonia
The solubility of the silver halides in ammonia decreases in the following order:
AgF > AgCl > AgBr >AgI
Silver halides become less soluble down the group

35. Effect of sunlight on the silver halides
AgCl
AgBr
AgI
Effect of sunlight
White precipitate turns purple/grey
Cream precipitate turns green/ yellow
No effect

36. Complete the following table describing chemical tests for the following species:
Formula
Name
Chemical test
Positive result
Cl2
Br2 I2
Cl-
Br- I-

37. Reducing Ability of the Halide Ions
Wednesday 19th January
Reducing Ability of the Halide Ions
This lesson we will…
Carry out a practical task to determine the reducing ability of the halide ions

38. Intro Questions Which halogen is the best oxidising agent?
Write the half-equations for the reduction of Cl2, Br2 and I2.
Which halide ion do you think would be the best reducing agent?

39. What is the oxidation number of sulphur in these different compounds?
H2S
H2SO4 S -2 +6
SO2 +4

40. The reaction of the metal halides with concentrated sulphuric acid is a method we can used to distinguish between the halides. The reaction is dependent on the reducing power of the halogens. We may observe sulphur in a variety of different oxidation states.

41. Reaction of Metal Halides with Sulphuric Acid
You must carry out this method for KCl, KBr, KI
Put half a spatula of the metal halide in a test tube.
Add a few drops of concentrated sulphuric acid.
Note down any observations
Dip a stirring rod in a bottle of ammonia and hold above the test tube. Note observations.
Try to identify the products formed

42. What could be formed? The hydrogen halides: HCl, HBr, HI
These would all produce white steamy fumes which produce white smoke with ammonia
The halogens: Cl2, Br2, I2
Cl2: green gas – distinctive smell
Br2: brown liquid or fumes when heated
I2: black solid / purple fumes
Sulphur dioxide: SO2
This is a colourless gas with a choking smell
Hydrogen sulphide: H2S
This is a colourless gas which smells of rotten eggs!
Sulphur: S
This is a yellow solid

43. What did you observe? KCl and H2SO4
Steamy fumes - white smoke when mixed with ammonia
KBr and H2SO4
Steamy fumes - white smoke when mixed with ammonia
Brown fumes
Yellow solid
KI and H2SO4
Steamy fumes - white smoke when mixed with ammonia
Black solid, purple fumes
Rotten egg smell
Which halide ion do you think is the strongest reducing agent?
Can you put the halides in order of reducing ability?

44. Reducing power of the halide ions:
Cl-
Br- I-
Stronger reducing agents as you go down the group
Use oxidation numbers to demonstrate how your observations show this

45. Reactions of the hydrogen halides
NH3 (g) + HCl (g) → NH4Cl (s) NH3 (g) + HBr (g) → NH4Br (s) NH3 (g) + HI (g) → NH4I (s)

46. Summary of Redox and the Halogens
Tuesday 25th January
Summary of Redox and the Halogens

47. aluminium chlorate (I)
What is the ionic fomula for:
NaClO
sodium chlorate (I)
Ca(ClO3)2
calcium chlorate (V)
AlCl3
aluminium chloride
Al(ClO)3
aluminium chlorate (I)
LiClO3
lithium chlorate (V)

48. TUESDAY 25TH JANUARY
Review of Redox and the Halogens
WEDNESDAY 26TH JANUARY
Practical on Iodine – Thiosulphate titration
TUESDAY 1ST FEBRUARY
Redox and the Halogens TEST
WEDNESDAY 2ND FEBRUARY
Iodine – Thiosulphate Titration ASSESSED PRACTICAL

49. Things to do this lesson
Review homeworks on half-equations and redox equations – ask for help if needed
Complete exam questions on redox and the halogens
Prepare revision notes on reactions of the halogens:
Physical state and colour of the halogens
Colours of the halogens dissolved in a hydrocarbon solvent
Halogens with Metal halides: demonstrating oxidising ability of the halogens
Silver nitrate with Metal halides, then ammonia: distinguishing between different halide ions
Conc. Sulphuric acid with solid metal halides: demonstrating reducing ability of the halide ions
Use your objectives sheet to check what you should know for this topic.