A blank nine-step write-up with the correct table headings. Print it for a real lesson and fill it in by hand. See the specimen lab book
Blank write-up: Identifying ions
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Study Hack Lab
RP 7 · Chemistry
Identifying ions
Write-up template
Name
Date
Course
GCSE Chemistry
Board and specification
AQA GCSE Chemistry (8462), 4.8.3Apparatus and techniques: AT 2, AT 8
Class and teacher
Aim
See the result of each test on known solutions. Then use flame tests, sodium hydroxide, and the carbonate, halide and sulfate tests to identify the ions in three unknown single ionic compounds.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
Each ion has its own test. Metal ions give flame colours and coloured hydroxide precipitates; carbonates fizz with acid, giving carbon dioxide. Halides give silver halide precipitates (white, cream, yellow); sulfates give white barium sulfate. Acid goes in first to remove carbonate, and it must not add the ion being tested for.
Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
Variables
Independent (you change)
Dependent (you measure)
Control (you keep the same)
Prediction
What colour will potassium chloride give in a flame test?
Silver nitrate is added (after nitric acid) to chloride, bromide and iodide solutions. What colours are the precipitates, in that order?
Aluminium, calcium and magnesium ions all give a white precipitate with a little sodium hydroxide. What happens when more sodium hydroxide is added?
Risk assessment
Hazard
Harm it could cause
Control
2 Apparatus
Safety goggles Protect your eyes from the reagents.
Bunsen burner and heatproof mat The hot blue flame for the flame tests.
Nichrome wire loop in a handle, and emery paper Carries a little of each solution into the flame; the emery paper cleans it.
Lithium, sodium, potassium, calcium and copper(II) chloride solutions, 0.4 mol/dm³ Known solutions for the flame tests.
Sodium carbonate, chloride, bromide, iodide and sulfate solutions, 0.4 mol/dm³ Known solutions for the tests for negative ions.
Unknown solutions A, B and C Each is one ionic compound for you to identify.
Test tubes in a rack About 1 cm depth of each solution for each test.
Teat (dropping) pipettes Add the reagents drop by drop and move the gas into the limewater.
Limewater (calcium hydroxide solution) Turns milky with carbon dioxide.
Dilute hydrochloric and nitric acids (0.4 mol/dm³), sodium hydroxide (0.4 mol/dm³), silver nitrate (0.05 mol/dm³) and barium chloride (0.1 mol/dm³) solutions The test reagents, in dropping bottles.
White tile Stood behind the tubes so the colours of the precipitates are easy to see.
Residue bottle Silver and barium mixtures go here, not down the sink.
3 Method
Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.
4 Results
The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.
Flame tests · Wire held at the edge of the blue Bunsen flame.
Solution
Flame colour
Lithium chloride (known)
Sodium chloride (known)
Potassium chloride (known)
Calcium chloride (known)
Copper(II) chloride (known)
Unknown A
Unknown B
Unknown C
Tests for negative ions: known sodium salts
Test
Solution
Observation
Gas transferred in pipettes
Dilute hydrochloric acid; gas into limewater
Dilute nitric acid, silver nitrate
Dilute nitric acid, silver nitrate
Dilute nitric acid, silver nitrate
Dilute hydrochloric acid, barium chloride
Unknowns A, B and C · Sodium hydroxide added a few drops at a time, then in excess.
Unknown
Sodium hydroxide
Dilute acid; limewater
Dilute nitric acid, silver nitrate
Dilute hydrochloric acid, barium chloride
A
B
C
Anomalies
Ring any anomalous result. Say what probably went wrong and whether you repeated it.
5 Graph
This practical has no graph: summarise your results in a sentence.
6 Analysis
Identify A, B and C
Answer
7 Conclusion and evaluation
Conclusion
Conclusion: what do your results show? Use your own numbers.
Sources of error
For each, say whether it is systematic or random, and how it affected your results.
A wire not cleaned between flame tests
Sodium from fingers, the bench or the tap water on the loop
The yellow (safety) flame
Hydrochloric acid added before the silver nitrate
Sulfuric acid, or no acid, before the barium chloride
Sodium hydroxide not added drop by drop and then in excess
Only one pipette of gas bubbled through the limewater
Judging similar colours by eye (cream and white; crimson and orange-red)
Iron(II) hydroxide turning brown at the surface
Improvement
How could you improve the method? Say why it would help.
8 Make safe and clear up
Turn off the Bunsen at the gas tap
Leave the hot wire to cool on the heatproof mat before you put it away
Pour the silver and barium mixtures into the residue bottle, not down the sink
Rinse the test tubes and stand them upside down in the rack to drain