Card 1: Reactions of the halide ions with silver nitrate.
Background
The three halide ions, chloride, bromide, and iodide, can be identified using a simple
test tube reaction with acidified silver nitrate.
Safety
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
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Concentrated Ammonia solution CORROSIVE.
Wear chemical splash-proof eye protection and nitrile gloves.
Use a fume cupboard.
Dilute nitric acid is an IRRITANT, at 0.5 mol dm–3
Method
1 Add 2 cm3 of each potassium halide solution into 3 separate test tubes. Note:
remember to rinse the measuring cylinder with distilled water before measuring
each different solution.
2 Add a mixture of 2 cm3 of silver nitrate solution and 1 cm3 of dilute nitric acid to
each test tube. Record your observations in the table below.
3 Add dilute ammonia solution drop wise to each test tube in turn until there is no
further change.
4 Repeat steps 1 to 3 but use concentrated ammonia solution in place of dilute
ammonia solution in step 3.
Results – draw this table and add your observations
Halide ion
solution
Observation on
adding AgNO3(aq)
Name and
formula of
precipitate
Observation on
adding NH3(aq)
Trend in
solubility of
silver halides
Chloride
Cl−(aq)
Bromide
Br−(aq)
Iodide
I−(aq)
Questions – use these to add this information to your mind map.
1
2
3
4
From your observations, complete the table to indicate the trend in solubility of the silver halides.
Construct a full equation and an ionic equation for the reaction of each potassium halide solution
with silver nitrate solution. Include state symbols.
a
silver nitrate  potassium chloride
b
silver nitrate  potasium bromide
c silver nitrate  potassium iodide
a State a general ionic equation with state symbols using X −(aq) as the halide ion.
b Explain how you can use these three reactions to test for the presence of a halide ion.
c Explain why silver nitrate solution is acidified before it is added to the halide solutions.
When distinguishing between the different halide ions, ammonia solution is often added after the
silver nitrate. Explain why this is done.
Card 2: Reactions of the halide ions with concentrated
sulfuric acid
Background
The three halide ions, chloride, bromide, and iodide, can all act as reducing agents,
when they are oxidised to the corresponding halogen. The trend in reducing ability can
be illustrated by observing how they react with concentrated sulfuric acid.
When sulfuric acid is reduced, different products can be formed depending on the
strength of the reducing agent.
Possible products are:
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sulfur dioxide (SO2) , an acidic gas with a choking smell
sulfur which is a yellow solid
hydrogen sulfide (H2S), a gas which smells of bad eggs.
Safety
Concentrated sulfuric acid CORROSIVE
This should be carried out in a fume cupboard using small quantities of chemicals.
Wear chemical splash-proof eye protection and nitrile gloves.
Gases produced are toxic and corrosive.
Method (In a fume cupboard)
1
2
3
Put 0.30 g of solid sodium chloride in a test tube, and carefully add five drops of
concentrated sulfuric acid. Test the gaseous product with damp blue litmus paper
held at the mouth of the test tube and note the colour of both the vapour and the
contents of the test tube.
Repeat the experiment but this time use solid sodium bromide in place of the
sodium chloride.
Repeat the experiment a third time using solid sodium iodide in place of sodium
chloride.
Results – draw this table and add your observations
Sodium
halide
Observations
Gases
Contents of test tube
Name of
products
Sodium
chloride
Sodium
bromide
Sodium
iodide
PTO – the questions are on the back!
Trend in reducing
ability of halide ions
Questions – use these to add this information to your mind
map.
4
a
When sodium halides react with concentrated sulfuric acid, a displacement
reaction occurs in which the corresponding hydrogen halide is produced along
with sodium hydrogen sulfate (NaHSO4). Construct an equation for the reaction
between sodium chloride and sulfuric acid. Include state symbols.
b Which observation tells you that the hydrogen chloride gas has been produced?
c How do you know that chloride ions have not been oxidised?
5
NaBr and NaI also take part in a redox reaction with concentrated sulfuric acid.
State in terms of oxidation states what is meant by:
a oxidation
b reduction
6
When sodium bromide reacts with concentrated sulfuric acid, bromide ions are
oxidised to bromine, and sulfuric acid is reduced to sulfur dioxide (SO2)
a Which observations tell you that these products are formed?
b Deduce the change in oxidation number of (i) bromine and (ii) sulfur in this
reaction
c Construct half equations for the formation of:
i bromide ions to bromine
ii concentrated sulfuric acid to sulfur dioxide.
d Combine the two half equations to construct an equation for the oxidation of
bromide ions by concentrated sulfuric acid.
Card 3: Reactions of the halides with potassium halides.
You are going to investigate how the halides react with potassium halides to infer any differences in
reactivity. You will need your prior understanding of displacement to work this out.
Safety
Wear eye protection. Do not breathe chlorine gas.
Method:
1. Put a piece of Universal Indicator paper onto a white tile.
2. Use a glass stirring rod to transfer a few drops of the first solution onto the indicator paper.
3. Repeat this with a fresh piece of paper and the different solutions.
4. In a test-tube, add some chlorine solution to a solution of potassium bromide.
5. Add some chlorine solution to a solution of potassium iodide.
6. Now try mixing solutions of bromine and potassium iodide. If there is time, mix the other
combinations of solutions to complete the table.
Results – draw this table and add your observations
Halogen
Effect on indicator
Reaction with KCl
Reaction with KBr
Reaction with KI
paper
solution
solution
solution
Chlorine water
Bromine water
Iodine water
Questions – use these to add this information to your mind map.
1. Which halogen solution is the strongest bleaching agent?
2. Which halogen is the most reactive?
3. Write a word and symbol equation for the reaction of chlorine with potassium bromide.
Card 4: Physical properties of the halogens.
Observations of the halogens
At this station you just need to make observations of the halogens, including its colour and state under
standard conditions. You could do this by taking photos or by noting down and adding this information
to your mind map.
Solubilities of halogens in water and in cyclohexane
Put 0.5 cm3 of chlorine water into one test tube, 0.5 cm3 of bromine water into a second test tube,
and 0.5 cm3 of iodine solution into a third test tube. Add 0.5 cm3 of cyclohexane to each test tube.
Shake the tubes and take photographs to show both layers in the tubes and add this information to
your mind map.
Questions – use these to add this information to your mind map.
1. How do the colours of the halogens change down the group? Comment on why you think the
colours change down the group.
2. Why do you think the state of the halogens under standard conditions change down the group.
3. Use your observations in the experiments on the solubilities of halogens to comment on the
relative solubility of halogens in water and in cyclohexane.
4. When and why might it be useful to make use of the solubility of bromine and iodine in
cyclohexane?