AQA GCSE Chemistry (8462), Higher tier · Chemical analysis › Identification of ions
Practise Halides. 19 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Required practical:Identifying ions (method, variables and exam tips)
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Halide ions in solution can be identified using a precipitation test. Give the colour of the precipitate formed by chloride ions.
white
Write the ionic equation for the reaction between silver ions and iodide ions. Include state symbols.
Ag+(aq) + I−(aq) → AgI(s)
Give the formula of the precipitate formed when silver nitrate solution reacts with potassium chloride solution.
AgCl
Complete the equation for the reaction of sodium iodide solution with silver nitrate solution. NaI(aq) + AgNO3(aq) → ....................(s) + NaNO3(aq)
AgI
Name the acid that is added before the silver nitrate solution in the test for halide ions.
(dilute) nitric acid
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Halide ions in solution can be identified using a precipitation test.
(a) Which solution is added in the test for halide ions? Tick (✓) one box.[1]
Barium chloride solution
Limewater
Silver nitrate solution
Sodium hydroxide solution
(b) Give the colour of the precipitate formed by chloride ions.[1]
(c) Give the colour of the precipitate formed by bromide ions.[1]
(d) A solution forms a yellow precipitate in the test. Name the halide ion in the solution.[1]
Show the answer and mark scheme
(a)Answer: Silver nitrate solution
(b)Answer: white
white
(c)Answer: cream
cream
(d)Answer: iodide
iodide / I−
Question 2Medium5 marks
In the test for halide ions, dilute nitric acid is added to the solution, followed by silver nitrate solution.
(a) Why is dilute nitric acid added first?[1]
(b) Explain why dilute hydrochloric acid must not be used instead of dilute nitric acid.[2]
(c) A student tested a solution of potassium bromide. Give the result and name the precipitate formed.[2]
Show the answer and mark scheme
(a)
to remove / react with carbonate ions (which would also form a precipitate with silver nitrate)
(b)
hydrochloric acid contains chloride ions
which would form a white precipitate (of silver chloride) whatever the sample contained
(c)
cream precipitate
silver bromide
Question 3Hard6 marks
Silver nitrate solution is used to test for halide ions.
(a) Write the ionic equation for the reaction between silver ions and iodide ions. Include state symbols.[2]
(b) Silver nitrate solution reacts with sodium bromide solution. AgNO3(aq) + NaBr(aq) → AgBr(s) + NaNO3(aq) Identify the spectator ions in this reaction.[1]
(c) A student added silver nitrate solution to a solution that contained both chloride ions and iodide ions. Suggest why the student could not identify both halide ions from the colour of the precipitate.[1]
(d) Another student added silver nitrate solution to a solution of an unknown salt without adding dilute nitric acid first. A white precipitate formed. The student concluded that the salt contained chloride ions. Explain why this conclusion may be wrong.[2]
Show the answer and mark scheme
(a)Answer: Ag+(aq) + I−(aq) → AgI(s)
Ag+ + I− → AgI
(aq) (aq) → (s)
(b)Answer: Na+ and NO3−
sodium ions and nitrate ions / Na+ and NO3− (both needed)
(c)
the two precipitates form together / mix so the yellow colour would hide the white
(d)
the salt could contain carbonate ions (instead)
carbonate ions also form a precipitate with silver ions if they are not removed by nitric acid