Laboratory Tests

Common Laboratory Tests

This is a list of some qualitative laboratory tests that can be used to identify unknowns in lab. These are simple tests leading to the identification of a few anions and cations and some common gases. Also included here is flame test information for selected cations.

Testing for anoins
Testing for cations
Flame test for cations
Tests for some common gases

Tests for Anions
Anion Symbol Test Results

Bromide Br^- Add silver nitrate solution to a solution of substance in dilute nitric acid Pale yellow precipitate, dissolves slightly in ammonia solution.

Carbonate CO₃^2-
a)Add dilute hydrochloric acid to the substance.

b)Add drop of phenolphthalein to a solution of substance.

Carbon dioxide gas is given off.

Turns bright pink (HCO₃ turns light pink).

Chloride Cl^- Add silver nitrate to a solution of substance in dilute nitric acid. Thick white precipitate dissolves in ammonia solution.

Hydrogen-
carbonate HCO₃^2-
a)Add dilute hydrochloric acid to the substance.

b)Add drop of phenolphthalein to a solution of substance.

Carbon dioxide gas is given off.

Turns light pink (CO₃^2- turns bright pink).

Iodide I- Add silver nitrate to a solution of substance in dilute nitric acid. Pale yellow precipitate, does not dissolve in ammonia solution.

Nitrate NO₃^- Add iron(II) sulfate solution followed by concentrated sulfuric acid to the solution Brown ring forms at the junction of the two liquids.

Sulfate SO₄^2- Add solution of barium chloride to the solution. White precipitate, does not dissolve in dilute hydrochloric acid.

Sulfite SO₃^2- Add solution of barium chloride to the solution. White precipitate, does dissolve in dilute hydrochloric acid.

Sulfide S^2- Add lead(II) ethanoate solution to the solution. Black precipitate

**Tests for Anions**
Anion	Symbol	Test	Results
Bromide	Br^-	Add silver nitrate solution to a solution of substance in dilute nitric acid	Pale yellow precipitate, dissolves slightly in ammonia solution.
Carbonate	CO₃^2-	a)Add dilute hydrochloric acid to the substance. b)Add drop of phenolphthalein to a solution of substance.	Carbon dioxide gas is given off. Turns bright pink (HCO₃ turns light pink).
Chloride	Cl^-	Add silver nitrate to a solution of substance in dilute nitric acid.	Thick white precipitate dissolves in ammonia solution.
Hydrogen- carbonate	HCO₃^2-	a)Add dilute hydrochloric acid to the substance. b)Add drop of phenolphthalein to a solution of substance.	Carbon dioxide gas is given off. Turns light pink (CO₃^2- turns bright pink).
Iodide	I-	Add silver nitrate to a solution of substance in dilute nitric acid.	Pale yellow precipitate, does not dissolve in ammonia solution.
Nitrate	NO₃^-	Add iron(II) sulfate solution followed by concentrated sulfuric acid to the solution	Brown ring forms at the junction of the two liquids.
Sulfate	SO₄^2-	Add solution of barium chloride to the solution.	White precipitate, does not dissolve in dilute hydrochloric acid.
Sulfite	SO₃^2-	Add solution of barium chloride to the solution.	White precipitate, does dissolve in dilute hydrochloric acid.
Sulfide	S^2-	Add lead(II) ethanoate solution to the solution.	Black precipitate

Tests for Cations
Cation Symbol Test Results

Aluminum Al³⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

White precipitate that dissolves as more sodium hydroxide solution is added.

White precipitate that does not dissolve as more ammonia solution is added.

Ammonium NH₄⁺ Add sodium hydroxide solution to a solution of the substance and gently heat. Ammonia gas is given off.

Calcium Ca²⁺
Add dilute sulfric acid to a solution of the substance

Also try flame test
White precipitate formed.

Copper (II) Cu²⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

Also try flame test

Pale blue precipitate that dissolves as more sodium hydorxide is added.\.

Pale blue precipitate, changing to deep blue solution as more ammonia is added.

Iron(II) Fe²⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

Pale green precipitate formed.

Pale green precipitate formed.

Iron(III) Fe³⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

Red-brown precipitate formed.

Red-brown precipitate formed.

Lead(II) Pb²⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

Use flame test to distinguish between lead and alumminum.

White precipitate, that does dissolve as more sodium hydroxide is added.

White precipitate that does not dissolve as more ammonia is added.

Magnesium Mg²⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

White precipitate, that does not dissolve as more sodium hydroxide is added.

White precipitate that does not dissolve as more ammonia is added.

Zinc Zn²⁺
a)Add dilute sodium hydroxide solution to a solution of the substance.

b)Add dilute ammonia solution to a solution of the substance.

White precipitate, that dissolve as more sodium hydroxide is added.

White precipitate that dissolve as more ammonia is added.

**Tests for Cations**
Cation	Symbol	Test	Results
Aluminum	Al³⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance.	White precipitate that dissolves as more sodium hydroxide solution is added. White precipitate that does not dissolve as more ammonia solution is added.
Ammonium	NH₄⁺	Add sodium hydroxide solution to a solution of the substance and gently heat.	Ammonia gas is given off.
Calcium	Ca²⁺	Add dilute sulfric acid to a solution of the substance Also try flame test	White precipitate formed.
Copper (II)	Cu²⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance. Also try flame test	Pale blue precipitate that dissolves as more sodium hydorxide is added.\. Pale blue precipitate, changing to deep blue solution as more ammonia is added.
Iron(II)	Fe²⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance.	Pale green precipitate formed. Pale green precipitate formed.
Iron(III)	Fe³⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance.	Red-brown precipitate formed. Red-brown precipitate formed.
Lead(II)	Pb²⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance. Use flame test to distinguish between lead and alumminum.	White precipitate, that does dissolve as more sodium hydroxide is added. White precipitate that does not dissolve as more ammonia is added.
Magnesium	Mg²⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance.	White precipitate, that does not dissolve as more sodium hydroxide is added. White precipitate that does not dissolve as more ammonia is added.
Zinc	Zn²⁺	a)Add dilute sodium hydroxide solution to a solution of the substance. b)Add dilute ammonia solution to a solution of the substance.	White precipitate, that dissolve as more sodium hydroxide is added. White precipitate that dissolve as more ammonia is added.

Flame Tests
Metal Symbol Flame Color

Barium Ba Yellow-green

Calcium Ca Red

Copper Cu Green

Lead Pb Blue

Lithium Li Pink

Potassium K Lilac

Sodium Na Orange

**Flame Tests**
Metal	Symbol	Flame Color
Barium	Ba	Yellow-green
Calcium	Ca	Red
Copper	Cu	Green
Lead	Pb	Blue
Lithium	Li	Pink
Potassium	K	Lilac
Sodium	Na	Orange

Tests to identify gases
Gas Symbol Test Results

Carbon dioxide CO₂ bubble gas through limewater (calcium hydroxide solution) Turns limewater cloudy.

Hydrogen H₂ Put a lighted splint into a sample of the gas. Burns with a "popping" sound

Oxygen O₂ Put a glowing splint into a sample of the gas. Splint relights.

**Tests to identify gases**
Gas	Symbol	Test	Results
Carbon dioxide	CO₂	bubble gas through limewater (calcium hydroxide solution)	Turns limewater cloudy.
Hydrogen	H₂	Put a lighted splint into a sample of the gas.	Burns with a "popping" sound
Oxygen	O₂	Put a glowing splint into a sample of the gas.	Splint relights.

Anion - An ion with a negative charge, formed when an atom gains electrons in a reaction (it now has more electrons than protons). Non-metals tend to form anions.

Cation - An ion with a positive charge, formed when an atom loses electrons in a reaction (it now has more protons than electrons). Hydrogen and metals tend to form cations.