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Test for chlorine identification and procedure

Chemical analysis • Identification of common gases

Key concepts

What you'll likely be quizzed about

  • Chlorine is a toxic, pale greenish-yellow gas at room temperature, irritating the eyes, throat, and lungs.
  • It dissolves slightly in water, reacting to form acidic and oxidizing species that produce characteristic reactions with indicators.
  • The green color may be challenging to observe at lower concentrations, so visual indicators are crucial for accurate identification.

Flashcards

Test your knowledge with interactive flashcards

What effect does low chlorine concentration have on test results?

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It produces slower or fainter color changes and might not show clear bleaching.

Key notes

Important points to keep in mind

Damp blue litmus paper turns red then bleaches white in chlorine's presence.

Moisture is essential: dry paper does not show the initial red change.

Hydrolysis (Cl2 + H2O ⇌ HCl + HClO) causes the acid effect; HClO leads to bleaching.

Low chlorine concentrations can give slow or faint changes.

Other oxidizing gases can bleach dyes, leading to false positives.

Conduct tests in a fume cupboard or well-ventilated area due to chlorine's toxicity.

Avoid direct inhalation from the test apparatus; hold indicator paper at a safe distance.

Visible greenish-yellow color supports identification but is typically unclear at low concentrations.

Contamination or pre-acidified paper can hide the initial color change.

Record both the sequence and timing of changes for accurate identification.

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