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Testing for common gases

Testing for common gases

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Explainer Video

Tutor: Alisha

Summary

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.


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Learn with Basics

Learn the basics with theory units and practise what you learned with exercise sets!
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Ions and their formation

Unit 1

Ions and their formation

Flame tests and flame emission spectroscopy

Unit 2

Flame tests and flame emission spectroscopy

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Testing for common gases

Unit 3

Testing for common gases

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FAQs - Frequently Asked Questions

How do you test for chlorine with litmus paper?

You can test for chlorine by dipping damp blue litmus paper into the solution. If chlorine is present the paper will be bleached.

How do we know a hydrogen is produced during a reaction?

You can identify if hydrogen is produced during a reaction by holding a lit splint at the mouth of test tube you will hear a 'squeaky pop' sound if hydrogen is present.

What is limewater?

Limewater is an aqueous solution of calcium hydroxide.

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