📖 Characteristic Tests for Gases
Gas Color & Odor Chemical Test Result
Hydrogen (H₂) Colorless, odorless Introduce burning splint Burns with a 'pop' sound
Oxygen (O₂) Colorless, odorless Introduce glowing splint Relights the glowing splint
Carbon Dioxide (CO₂) Colorless, odorless Pass through Lime water Turns milky (insoluble CaCO₃)
Ammonia (NH₃) Colorless, pungent smell Pass through Nessler's Reagent Gives a brown precipitate/color
Chlorine (Cl₂) Greenish-yellow, pungent Moist starch iodide paper Turns blue-black

Select Unknown Gas Tube

Apply Test

A test that shows no change only rules a gas out. Look for the one positive (confirmatory) result, then record your inference.

Safety Notes

  • Hydrogen is flammable: keep the burning-splint test small and away from the gas supply.
  • Chlorine and ammonia are toxic/pungent: test in a fume cupboard and never inhale directly — waft gently if instructed.
  • Nessler's reagent contains mercury and is toxic; handle with care and collect waste as directed.
  • Point tube mouths away from yourself and others when introducing a splint.
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Working Inference

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Run at least one test, choose a likely gas, and write your evidence before revealing the identity.
Lab Journal
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Test Result---
Gas Identified???