C3 4.1a – Student practical sheet
Flame tests
When placed in a roaring Bunsen flame different metal ions will produce different coloured flames.
This allows different metals to be distinguished from the flame colours they produce. Flame tests
can be used to identify a metal ion in an unknown compound. This can be particularly useful in
forensic science and chemical analysis relating to health and environmental issues.
Aim
To be able to identify different metal ions by their flame colour.
Equipment
●
eye protection
●
pipettes
●
Bunsen burner
●
●
heat proof mat
solid samples containing different metal
ions
●
hydrochloric acid (2 mol/dm )
●
splint
●
nichrome wire
●
watch glasses
3
Safety
●
Make sure you wear your eye protection throughout the experiment.
●
Barium compounds are harmful. Avoid skin contact and wash with water if any gets on your
hands.
●
Hydrochloric acid is an irritant. Rinse with cold water if there is skin contact.
●
Be careful when dipping the hot wire in the acid, it may splatter your skin.
●
Ensure all long hair is tied back and away from the Bunsen burner flame.
What you need to do
1
Create a suitable results table to record each solid metal ion sample and the flame colour.
2
Take a piece of nichrome wire and make a loop at one end.
3
Dip the wire in hydrochloric acid to clean it.
4
Place a small amount of one of the solids provided onto a watch glass.
5
Roll the loop of the nichrome wire in the solid, so it coats the wire.
6
Place the wire loop containing the solid sample into a roaring blue Bunsen burner flame and
record the colour of the flame produced.
7
Dip the nichrome wire in the hydrochloric acid to remove the remaining solid sample.
8
Repeat the procedure with the next solid sample.
Using the evidence
1
Make a complete list of the metal ions and their corresponding flame colour. (5 marks)
Extension
2
Use some other metal ion samples which you have not used already and investigate their
flame colours.
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C3 4.1b – Student practical sheet
Metal ion solutions
Aim
To be able to identify different metal ions by their flame colour.
Equipment
●
eye protection
●
Bunsen burner
●
range of metal ion solutions – lithium, sodium,
potassium, calcium and barium
Safety
●
Make sure you wear your eye protection throughout the demonstration.
What you need to do
1
Watch the demonstration carefully, paying attention to the flame colours produced by each
solution when it is sprayed into the flame.
2
Draw out a suitable results table listing the metal ions used and the flame colours which are
produced.
Using the evidence
1
Make a complete list of the metal ion solutions and the corresponding flame colour. (5 marks)
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333
C3 4.1c – Student practical sheet
Precipitation reactions
When two solutions are mixed together, a solid may be produced, which is called a precipitate.
When certain solutions which contain a particular metal ion are reacted with sodium hydroxide
solution, they produce a coloured precipitate.
Aim
To be able to identify different metal ions in solution using sodium hydroxide solution.
Equipment
●
eye protection
●
teat pipettes or dropper bottles
●
test tube rack
●
test tubes
●
metal ion solutions (aluminium, magnesium,
calcium, copper(II), iron(II) and iron(III) ions)
●
sodium hydroxide solution (2 mol/dm )
3
Safety
●
Wear your eye protection throughout the experiment.
●
Sodium hydroxide solution is corrosive and may cause severe damage to eyes. If any gets on
your skin it off with water.
What you need to do
1
Draw out a suitable results table showing the metal ions used and the colours of the
precipitates which are formed.
2
Using a pipette, fill a test tube to around 2 cm depth with a metal ion solution.
3
With a different pipette, add a few drops of sodium hydroxide solution to the metal ion solution
and shake the test tube gently.
4
Look at the test tube, a precipitate should have been formed. Write down the colour in your
results table.
5
If the precipitate is white, add more sodium hydroxide and watch to see if the precipitate
dissolves. Record your observations.
6
Repeat this procedure with each metal ion sample.
Using the evidence
1
Make a complete list of the metal ion solutions and the corresponding precipitate colour.
(6 marks)
Extension
2
Use some other metal ion samples which you have not used already and investigate the
colours of the precipitates which are formed.
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C3 4.1d – Student worksheet
Identifying metal ions
There are several different tests which can be used to identify metal ions. These include flame
tests, and the colours of the precipitates formed when sodium hydroxide solution is reacted with
solutions containing the metal ions.
1
2
3
4
Plan an investigation which could be used to distinguish between three white solid compounds
which include sodium chloride, magnesium chloride and potassium chloride.
a
Explain which tests you would need to carry out and indicate what equipment is required to
perform the tests. (3 marks)
b
Indicate how the results of the tests would allow you to identify each solid. (3 marks)
Explain how flame tests would be useful to distinguish between the following pairs of
compounds:
a
lithium chloride and sodium sulfate (1 mark)
b
barium chloride and lithium chloride (1 mark)
c
calcium chloride and potassium chloride. (1 mark)
Tests are carried out on a compound, A, in an attempt to prove its identity. Sodium hydroxide
solution is added to a solution of compound A which results in a brown precipitate being
formed.
a
Which ion present in compound A would cause the brown precipitate to form? State the
ion’s name and give its chemical symbol. (2 marks)
b
Give the name of the chemical compound present in the brown precipitate. (1 mark)
A chemical company wants to make a firework which mimics the colours of traffic lights (red,
yellow and green).
a
Suggest the names of three different compounds which the company could use to give the
required colours when they are heated. (3 marks)
b
Describe how you would carry out a flame test, using nichrome wire, to confirm that the
compounds which you have suggested would give the correct colours. (3 marks)
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C3 4.2a – Student practical sheet
Chemical tests for halide ions
Group 7 elements when joined in a compound with a metal are referred to as halides. When these
elements form ionic compounds they gain an electron and become negatively charged. These are
known as halide ions. In this practical you will identify chloride, bromide and iodide ions.
Aim
To be able to identify chloride, bromide and iodide ions through a simple chemical test with silver
nitrate.
Equipment
●
eye protection
●
silver nitrate solution
●
halide solutions – chloride, bromide and
iodide
●
teat pipettes or dropper bottles
●
test tube rack
●
nitric acid (2 mol/dm )
●
3 × test tubes
3
Safety
●
You must wear eye protection throughout the experiment.
●
Nitric acid is an irritant. Avoid contact with skin and rinse with water if any contact occurs.
●
Silver nitrate is corrosive and can stain skin – avoid all skin contact.
What you need to do
3
1
Use a pipette to transfer approximately 2 cm of one of the halide solutions provided into a
clean test tube.
2
Add an equal volume of nitric acid to the sample.
3
Then add a few drops of silver nitrate to the acidified halide solution.
4
Observe the colour of the precipitate and record your result in a suitable table.
5
Repeat the procedure with the other halide solutions.
Using the evidence
When the halide solution reacts with the silver nitrate solution, a solid substance is formed. This
solid is called a precipitate. The reactions produce silver halide precipitates, each with a different
colour. The general word equation for this reaction is:
silver nitrate + metal halide → silver halide + metal nitrate
1
Think carefully about each reaction you performed. Write down the names and formulae of
each of the metal halide samples which you used during the practical. (3 marks)
2
Write down three different word equations to represent each of the reactions which occurred.
Under each silver halide indicate the colour of the precipitate using your practical results to
help. (3 marks)
Extension
3
Using the formula of each metal halide which you used and the silver nitrate formula, AgNO3,
construct a balanced symbol equation for each of your reactions in question 2. (6 marks)
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C3 4.2b – Student practical sheet
Identifying an unknown negative ion
There are a range of simple chemical tests which can be performed on solutions containing
dissolved ionic compounds. The results may be used to confirm or eliminate certain negative ions.
Aim
To be able to identify the negative ion in an unknown chemical solution.
Equipment
●
eye protection
●
pipettes
●
barium chloride solution
●
silver nitrate solution
●
delivery tube
●
test tube rack
●
limewater
●
test tubes
●
nitric acid
●
unknown solution for testing
Safety
●
Eye protection must be worn throughout the experiment.
●
Nitric acid is an irritant. Avoid contact with skin and rinse with water if any contact occurs.
●
Silver nitrate is corrosive and can stain skin. Students should wear latex gloves.
What you need to do
1
Before you start the experiment, you need to produce a risk assessment (Hint: Look on the
labels of the bottles of the chemicals you will be using), and design a table to record your
results.
2
Find out the tests for carbonate ions, sulfate ions and halide ions and record each of the test
procedures.
3
Now carefully perform each test on the unknown solution until you get a positive test result.
Using the evidence
1
Identify the unknown negative ion in the solution. (3 marks)
2
Fully describe which test identified the negative ion and draw a diagram of the equipment used
for this test. (3 marks)
3
Write a word equation which represents the chemical reaction which has occurred during the
positive test result. (2 marks)
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337
C3 4.2c – Student practical sheet
Testing for carbonate ions
When carbonate ions react with an acid, carbon dioxide is produced as one of the products. By
testing for carbon dioxide after reacting the carbonate with an acid, we can show that the negative
ion is a carbonate ion.
Aim
To be able to test for a carbonate ion.
Equipment
●
eye protection
●
metal carbonate, e.g. calcium carbonate
in the form of marble chips
●
conical flask (100 ml)
●
delivery tube
●
pipettes
●
hydrochloric acid
●
rubber bung
●
limewater
●
test tube
●
test tube rack
Safety
●
Eye protection must be worn throughout the experiment.
●
Dilute hydrochloric acid is an irritant – wash immediately if contact is made with the skin.
What you need to do
1
Put three or four marble chips into a conical flask.
2
Half fill a test tube with limewater and stand it in a test tube rack.
3
Add 25 cm of hydrochloric acid to the conical flask.
4
Attach a delivery tube to the top of the conical flask and insert the other end into the limewater
and allow the gas to bubble into the limewater.
3
Using the evidence
1
Describe what happens to the limewater if carbon dioxide is bubbled through it. (2 marks)
2
Write a general word equation for a metal carbonate reacting with an acid. (1 mark)
3
Produce a word equation for the reaction between calcium carbonate and hydrochloric acid
which you used during your experiment. (1 mark)
4
Write a complete word equation for the reaction between sodium carbonate and nitric acid.
(1 mark)
Extension
5
Use a list of positive and negative ions to help construct fully balanced symbol equations for
questions 3 and 4. (6 marks)
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C3 4.2d – Student worksheet
Negative ions
2-
1
Describe a simple chemical test for carbonate ions, CO3 . (3 marks)
2
Write down the chemical formula of each of the following metal carbonates:
3
4
5
a
Calcium carbonate (1 mark)
b
Lithium carbonate (1 mark)
c
Potassium carbonate (1 mark)
d
Sodium carbonate (1 mark)
Answer the questions below.
a
Write a word equation for potassium carbonate reacting with sulfuric acid. (1 mark)
b
Write a balanced symbol equation for potassium carbonate reacting with sulfuric acid.
(2 marks)
A student was given a bottle of sodium sulfate solution, Na2SO4 (aq) and asked to perform a
test on the solution to prove it contained sulfate ions.
a
Name the solutions which the student should add to the sodium sulfate solution to provide
a positive test for sulfate ions. (2 marks)
b
Describe what would be observed if the test is positive. (1 mark)
c
Write the word equation for the reaction which has occurred. (1 mark)
d
Produce a balanced symbol equation for this reaction. (2 marks)
Three colourless solutions A, B and C are each tested to show that they contain a halide ion.
The results of the tests are shown below:
i
An acidified sample of solution A produces a cream precipitate when a few drops of silver
nitrate solution are added.
ii
An acidified sample of solution B produces a white precipitate when a few drops of silver
nitrate solution are added.
iii An acidified sample of solution C produces a yellow precipitate when a few drops of silver
nitrate solution are added.
Identify the halide ion present in each solution A, B and C. (3 marks)
6
A solid white compound has been found spilt on a laboratory desk from a previous lesson. The
teacher thinks the powder must be lithium carbonate, Li2CO3. Outline a series of simple
chemical tests which could be used to confirm that the compound is lithium carbonate.
(4 marks)
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339
C3 4.3a – Student practical sheet
Titration
When the right quantities of acid and alkali are reacted together a neutralisation reaction will occur.
If a known volume of acid is reacted with an alkali of known volume and concentration, then the
unknown concentration of the acid may be calculated.
Aim
To be able to perform a titration involving a strong acid and strong alkali and work out the unknown
concentration of the alkali.
Equipment
●
●
●
eye protection
burette and stand
3
conical flask (250 cm )
●
●
●
3
glass pipette (25 cm )
phenolphthalein
pipette filler
●
●
●
sodium hydroxide solution (approx.
3
0.1 mol/dm )
3
hydrochloric acid (0.1 mol/dm )
white tile
Safety
●
Make sure you wear eye protection throughout the experiment.
●
Both the acid and alkali are irritants and skin contact should be avoided.
●
Take care not to break the pipette when attaching the pipette filler.
What you need to do
1
Create a suitable results table to record the burette readings taken during the experiment.
2
Measure out 25 cm of sodium hydroxide solution using a glass pipette, with a pipette filler
attached to the top of the pipette.
3
Fill a burette with 0.1 mol/dm hydrochloric acid solution above the 0 mark. Then allow some
acid to run out so that the bottom of the meniscus is level with the 0 mark.
4
Place the conical flask on to a white tile and add 5 or 6 drops of phenolphthalein indicator to
the sodium hydroxide solution in the conical flask.
5
Add acid from the burette quite quickly, swirling the conical flask, until the indicator changes to
colourless.
6
Looking at the bottom of the meniscus, record the burette reading in your table.
7
Rinse out the conical flask thoroughly. Repeat the whole procedure, but when you have added
3
about 2 cm less acid than in your previous titration, start to add the acid slowly, drop-by-drop,
while swirling the flask. Stop adding the acid as soon as the solution becomes colourless.
8
Repeat the procedure, making sure you add the acid drop-by-drop when close to the end-point.
9
Stop when you have two results within 0.1 cm of each other.
3
3
3
Using the evidence
1
Explain why it is necessary to repeat the procedure. (1 mark)
2
Write the general word equation for an acid reacting with an alkali. (1 mark)
3
Write a word equation for the reaction which has occurred during the titration. (1 mark)
4
Write a balanced symbol equation for the reaction in question 3. (1 mark)
Extension
5
Using the information given, together with your results from the practical, calculate the exact
concentration of the alkali, sodium hydroxide. (2 marks)
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C3 4.3b – Student practical sheet
Planning a titration investigation
Aim
To plan an investigation to find out the exact concentration of a solution of nitric acid which is
3
approximately 0.1 mol/dm .
What you need to do
1
Your task is to produce a suitable plan for an experiment to find the exact concentration of a
3
solution of nitric acid which you are told has a concentration of approximately 0.1 mol/dm .
2
You will need to decide which suitable strong alkali to use and also a sensible concentration for
the solution. You will also need to decide on suitable volumes of solutions to use during the
experiment.
3
Your plan should include:
●
A risk assessment of the practical.
●
A list of equipment you would need.
●
A detailed method of how to carry out the titration in a step-by-step way.
●
A fully labelled diagram illustrating the practical set-up.
●
A results table with the correct headings for each column.
Extension
1
Get your teacher to check your plan. When it has been approved, carefully carry out your
experiment and record your results. (15 marks)
2
Use the results from your practical, together with the exact concentration of the strong alkali
solution, to calculate the exact concentration of the nitric acid. (3 marks)
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341
C3 4.3c – Student worksheet
Titration calculations
1
Sodium hydroxide and hydrochloric acid react together according to the equation:
NaOH + HCl → NaCl + H 2O
3
In a titration between sodium hydroxide solution and hydrochloric acid 25.0 cm of 0.2 mol/dm
3
sodium hydroxide solution is neutralised by 27.75 cm of hydrochloric acid.
3
3
Use the information to calculate the concentration of the hydrochloric acid in mol/dm . Give
your answer to 2 decimal places. (3 marks)
2
Sodium hydroxide and nitric acid react together according to the equation:
NaOH + HNO3 → NaNO3 + H2O
3
In a titration between sodium hydroxide solution and nitric acid 10.0 cm of 0.15 mol/dm
3
sodium hydroxide solution is neutralised by 12.0 cm of nitric acid.
3
3
Use the information to calculate the concentration of the nitric acid in mol/dm . Give your
answer to 3 decimal places. (3 marks)
3
Potassium hydroxide and hydrochloric acid react together according to the equation:
KOH + HCl → KCl + H2O
3
In a titration between potassium hydroxide solution and hydrochloric acid 10.0 cm of
3
3
0.1 mol/dm potassium hydroxide solution is neutralised by 0.12 mol/dm hydrochloric acid.
Use the information to calculate the volume of hydrochloric acid needed to exactly neutralise
the potassium hydroxide solution. Give your answer to 2 decimal places. (3 marks)
4
Potassium hydroxide and nitric acid react together according to the equation:
KOH + HNO3 → KNO3 + H2O
3
In a titration between potassium hydroxide solution and nitric acid 25.0 cm of 0.25 mol/dm
3
potassium hydroxide solution is neutralised by 0.2 mol/dm nitric acid.
3
Use the information to calculate the volume of nitric acid needed to exactly neutralise the
potassium hydroxide solution. Give your answer to 2 decimal places. (3 marks)
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C3 4.3d – Student worksheet
Further titration calculations
1
Potassium hydroxide and hydrochloric acid react together according to the equation:
KOH + HCl → KCl + H2O
3
In a titration between potassium hydroxide solution and hydrochloric acid 10.0 cm of
3
3
0.1 mol/dm potassium hydroxide solution is neutralised by 10.50 cm of hydrochloric acid.
3
Use the information to calculate the concentration of the hydrochloric acid in mol/dm . Give
your answer to 3 decimal places. (3 marks)
2
Potassium hydroxide and nitric acid react together according to the equation:
KOH + HNO3 → KNO3 + H2O
3
In a titration between potassium hydroxide solution and nitric acid 25.0 cm of 0.1 mol/dm
3
potassium hydroxide solution is neutralised by 19.35 cm of nitric acid.
3
3
Use the information to calculate the concentration of the nitric acid in mol/dm . Give your
answer to 3 decimal places. (3 marks)
3
Sodium hydroxide and hydrochloric acid react together according to the equation:
NaOH + HCl → NaCl + H 2O
3
In a titration between sodium hydroxide solution and hydrochloric acid 10.0 cm of 0.25 mol/dm
3
sodium hydroxide solution is neutralised by 0.16 mol/dm hydrochloric acid.
3
Use the information to calculate the volume of hydrochloric acid needed to exactly neutralise
the sodium hydroxide solution. Give your answer to 2 decimal places. (3 marks)
4
Sodium hydroxide and nitric acid react together according to the equation:
NaOH + HNO3 → NaNO3 + H2O
3
3
In a titration between sodium hydroxide solution and nitric acid 25.0 cm of 0.2 mol/dm sodium
3
hydroxide solution is neutralised by 0.32 mol/dm nitric acid.
Use the information to calculate the volume of nitric acid needed to exactly neutralise the
sodium hydroxide solution. Give your answer to 2 decimal places. (3 marks)
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343
C3 4.4a – Student practical sheet
Identifying an unknown compound
Using the knowledge which you have gained in recent lessons about testing for certain positive and
negative ions, use a series of chemical tests to identify an unknown compound.
Aim
To be able to identify an unknown compound by deciding on and carrying out a series of
appropriate chemical tests.
Equipment
●
A tray of equipment will be provided which contains all the equipment necessary to perform
appropriate chemical tests.
Safety
●
Eye protection must be worn throughout the experiments.
What you need to do
1
Create a risk assessment and suitable results table to record the data obtained before you start
any practical work.
2
Check your risk assessment with your teacher to ensure all possible hazards have been
identified before starting the practical work.
3
Decide on and carry out a series of appropriate tests for positive metal ions and negative ions,
limited to those which you have come across in previous lessons.
Using the evidence
1
Confirm the identity of both the positive and negative ions and then suggest the name of the
unknown compound. (3 marks)
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C3 4.4b – Student practical sheet
Planning a forensic investigation
An unknown white powder has been found by a forensic scientist at a crime scene.
Aim
To plan an investigation to confirm that the unknown white powder is barium chloride.
What you need to do
Your task is to produce a suitable plan for an experiment to confirm the identity of the unknown
white powder found at the crime scene.
1
Describe the chemical tests which you would carry out on the white solid in order to determine
if it is barium chloride. (4 marks)
2
Your plan should include:
a
A risk assessment of the practical. (4 marks)
b
A list of equipment and chemicals you would need. (4 marks)
c
A detailed method of how to carry out the tests in a step-by-step way. (4 marks)
Extension
Get the teacher to check your plan. When it has been approved, carefully carry out your
experiment.
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345
C3 4.4c – Student worksheet
Environmental report
An employee working for the local water authority has discovered traces of a white powder close to
a river in a beauty spot which is popular with walkers. Nearby there is a bottle on the ground which
is labelled as potassium carbonate. The bottle has a hazard label showing a black cross. The white
powder is sent to a laboratory for analysis and the results confirm that the white power, which has
come from the bottle, is potassium carbonate.
You have to imagine that you are the employee. Your task is to compile a memo which will be sent
to your boss describing the incident. In the memo, you must:
1
Explain what has happened and what action has been taken. (3 marks)
2
Give details of the simple chemical tests which the laboratory should perform to analyse the
substance (based on the tests used for identifying positive and negative ions in the
specification). (6 marks)
3
Give the results of these tests which confirm the ions which were present in the sample.
(2 marks)
4
Explain the hazards associated with this substance and the possible problems this poses to the
river and the wildlife which rely on the river to survive. (4 marks)
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C3 4.4d – Student worksheet
Analysing substances
3
3
3
1
25.0 cm of 0.30 mol/dm potassium hydroxide was exactly neutralised by 27.80 cm of
hydrochloric acid. Calculate the concentration of the hydrochloric acid, giving your answer to
2 decimal places. (2 marks)
2
A student carries out a titration using hydrochloric acid and potassium hydroxide solution.
3
4
a
Write a word equation for the reaction between potassium hydroxide and hydrochloric acid.
(1 mark)
b
One of the products produced in the reaction in question a is an ionic compound. Write the
formula of each of the ions present in this compound. (2 marks)
c
Describe how you could produce crystals of the ionic compound from the solution produced
during the titration. (1 mark)
d
Describe a test for each of the ions in the compound. Give the expected results which
would confirm the presence of each ion. (4 marks)
3
3
3
25.0 cm of 0.20 mol/dm nitric acid was exactly neutralised by 18.80 cm of sodium hydroxide
solution.
a
Write a symbol equation for the reaction between nitric acid and sodium hydroxide.
(1 mark)
b
Calculate the concentration of the sodium hydroxide solution, giving your answer to
2 decimal places. (2 marks)
When a solution of an ionic compound is sprayed into a roaring Bunsen burner flame a bright
yellow flame is produced. Further testing of the solution by acidifying it and adding silver nitrate
solution produces a cream precipitate.
a
Identify two ions which are present in the ionic compound. (2 marks)
b
Give the name of the ionic compound which is present in the spray. (1 mark)
c
Write a word equation for the reaction between the compound and silver nitrate solution.
(1 mark)
d
Write a fully balanced symbol equation for this reaction. (1 mark)
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