Testing for common gases

In a nutshell

Simple lab tests can be done to identify which gas is produced during a reaction. The table below summarises the tests you need to know.

Tests for common gases

Gas	test	Positive result
Chlorine	You can test for chlorine by dipping damp blue litmus paper into the solution.	Litmus paper is bleached
Oxygen	You can test if the gas produced is oxygen by holding a glowing splint inside test tube.	Splint relights
Carbon dioxide	You can identify if carbon dioxide is produced by bubbling the gas through limewater. *Note:* Limewater is an aqueous solution of calcium hydroxide.	Limewater turns cloudy
Hydrogen	You can identify if hydrogen is produced during a reaction by holding a lit splint at the mouth of test tube.	Hear a 'squeaky pop' sound

Example

A reaction results gas Y being produced. After carrying out the tests for gases it is found that all tests turned out to be negative excluding the test where the gas was bubbled through limewater. Upon bubbling the gas through limewater, the limewater turned cloudy. This shows that gas Y is carbon dioxide.