GCSE Chemistry revision

Flame tests

Identification of ions by chemical and spectroscopic means (chemistry only)

AQA 4.8.3.1 Foundation & Higher

Your specification

AQA student objectives

Learning pathway

ALL 🎯

MOST 🎯🎯

SOME 🎯🎯🎯

Revision summary

Read on screen, then print for Cornell-style active revision.

Loop Preparation: Dip a clean platinum or nichrome wire loop into concentrated hydrochloric acid and hold it in a hot, non-luminous (blue) Bunsen burner flame to clean off any impurities until no residual colour is observed.
Sample Testing: Dip the cleaned wire loop into the solid sample or aqueous solution containing the cation, place it into the edge of the blue Bunsen flame, and observe the distinct characteristic flame colour produced.

1. Flame Test Procedure and Method AQA

Loop Preparation: Dip a clean platinum or nichrome wire loop into concentrated hydrochloric acid and hold it in a hot, non-luminous (blue) Bunsen burner flame to clean off any impurities until no residual colour is observed.
Sample Testing: Dip the cleaned wire loop into the solid sample or aqueous solution containing the cation, place it into the edge of the blue Bunsen flame, and observe the distinct characteristic flame colour produced.

Lithium (Li⁺) and Sodium (Na⁺): Placing a sample containing lithium ions into the flame produces a distinctive red (crimson) flame, whereas sodium ions produce a bright, persistent yellow flame.
Example: Testing lithium chloride (LiCl) yields a crimson-red flame, while sodium chloride (NaCl) produces an intense yellow flame.
Potassium (K⁺): Potassium ions produce a characteristic lilac (pale violet) flame during testing.
Example: Testing potassium nitrate (KNO₃) generates a delicate lilac flame (which can be viewed through cobalt blue glass to mask trace yellow sodium impurities).

2. Identification of Group 1 Cations AQA

Lithium (Li⁺) and Sodium (Na⁺): Placing a sample containing lithium ions into the flame produces a distinctive red (crimson) flame, whereas sodium ions produce a bright, persistent yellow flame.
Example: Testing lithium chloride (LiCl) yields a crimson-red flame, while sodium chloride (NaCl) produces an intense yellow flame.
Potassium (K⁺): Potassium ions produce a characteristic lilac (pale violet) flame during testing.
Example: Testing potassium nitrate (KNO₃) generates a delicate lilac flame (which can be viewed through cobalt blue glass to mask trace yellow sodium impurities).

Calcium (Ca²⁺) and Barium (Ba²⁺): Calcium ions impart an orange-red (brick red) colour to the flame, while barium ions produce a light green (apple green) flame.
Example: Calcium carbonate (CaCO₃) burn tests produce an orange-red flame, whereas barium chloride (BaCl₂) gives an apple-green flame.
Copper(II) (Cu²⁺): Copper(II) ions give off a characteristic blue-green flame when heated in the Bunsen flame.
Example: Testing copper(II) sulfate (CuSO₄) or copper(II) nitrate (Cu(NO₃)₂) produces a brilliant blue-green flame.

3. Identification of Group 2 and Transition Metal Cations AQA

Calcium (Ca²⁺) and Barium (Ba²⁺): Calcium ions impart an orange-red (brick red) colour to the flame, while barium ions produce a light green (apple green) flame.
Example: Calcium carbonate (CaCO₃) burn tests produce an orange-red flame, whereas barium chloride (BaCl₂) gives an apple-green flame.
Copper(II) (Cu²⁺): Copper(II) ions give off a characteristic blue-green flame when heated in the Bunsen flame.
Example: Testing copper(II) sulfate (CuSO₄) or copper(II) nitrate (Cu(NO₃)₂) produces a brilliant blue-green flame.