AQA GCSE Chemistry (8462), Higher tier · Chemical analysis › Identification of ions
Practise Flame tests. 14 exam-style questions 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)
Quick recall
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Flame tests can be used to identify some metal ions. What colour flame is produced by potassium compounds?
lilac
One compound produced a lilac flame. Name the metal ion in this compound.
potassium
The student then looked at the flame through blue glass. The blue glass absorbs yellow light. The flame now looked lilac. Identify the other metal ion in the mixture.
potassium
Which metal compound should be added to the firework mixture?
a potassium compound
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Flame tests can be used to identify some metal ions.
(a) What colour flame is produced by potassium compounds?[1]
(b) Which metal ion gives a crimson flame? Tick (✓) one box.[1]
Calcium
Copper
Lithium
Sodium
(c) A compound gives a green flame. Name the metal ion in the compound.[1]
(d) What colour flame is produced by calcium compounds?[1]
Show the answer and mark scheme
(a)Answer: lilac
lilac
(b)Answer: Lithium
(c)Answer: copper(II)
copper(II) / copper / Cu2+
(d)Answer: orange-red
orange-red
Question 2Medium5 marks
A student carried out flame tests on four solid compounds using a wire loop and a Bunsen burner.
(a) Describe how the student should carry out a flame test on one of the solid compounds.[3]
(b) Explain why the wire loop must be cleaned before each test.[1]
(c) One compound produced a lilac flame. Name the metal ion in this compound.[1]
Show the answer and mark scheme
(a)
clean the wire loop by dipping it in (hydrochloric) acid and holding it in the flame (until there is no colour)
dip the loop into the solid (moistened with acid)
hold the loop in the (edge of a) blue / roaring Bunsen burner flame and record the colour
(b)
to remove traces of the previous compound, which would affect the flame colour
(c)Answer: potassium
potassium / K+
Question 3Hard5 marks
A student did a flame test on a white solid. The solid was a mixture of two compounds. The flame was bright yellow.
(a) The student concluded that the only metal ion in the mixture was sodium. Explain why the student's conclusion is not valid.[2]
(b) The student then looked at the flame through blue glass. The blue glass absorbs yellow light. The flame now looked lilac. Identify the other metal ion in the mixture.[1]
(c) Suggest why a flame test would not be a good way to show whether a solid contains both lithium ions and calcium ions.[1]
(d) Name an instrumental method that could identify all the metal ions in a mixture.[1]
Show the answer and mark scheme
(a)
sodium ions give a yellow flame so sodium is present
but the yellow colour can mask the colours of other metal ions (so another metal ion may be present)
(b)Answer: potassium
potassium / K+
(c)
the crimson and orange-red colours are similar / one colour could mask the other