Chlorine (Oxford AQA IGCSE Chemistry)

Revision Note

Alexandra Brennan

Written by: Alexandra Brennan

Reviewed by: Stewart Hird

Test for Chlorine Gas

  • The test for chlorine makes use of litmus paper

  • If chlorine gas is present, damp blue litmus paper will turn red and then be bleached white

  • It turns red initially as acids are produced when chlorine comes into contact with water

  • Chlorine also has a characteristic sharp, choking smell 

  • Chlorine should always be handled in a fume cupboard due to its toxicity

Testing for chlorine gas

The diagram shows damp blue litmus paper being placed into chlorine gas and then turning red before bleaching to a final white colour
Chlorine bleaches damp blue litmus paper white

Examiner Tips and Tricks

You should distinguish between properties of gases and tests for gases. Chlorine 'smells like swimming pools' is a characteristic, but it is not an acceptable means of identification. 

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Alexandra Brennan

Author: Alexandra Brennan

Expertise: Chemistry

Alex studied Biochemistry at Newcastle University before embarking upon a career in teaching. With nearly 10 years of teaching experience, Alex has had several roles including Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s passion for creating engaging content that enables students to succeed in exams drove her to pursue a career outside of the classroom at SME.

Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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