Tests for gases

Question 1

What’s the test and result for

Ammonia (NH₃)

Answer 1

Test: Hold damp red litmus paper (or Universal Indicator paper) in gas
Result: Indicator paper turns blue

Ammonia is colourless with a pungent smell.

Question 2

What’s the test and result for

Carbon dioxide (CO₂)

Answer 2

Test: Bubble gas through limewater (calcium hydroxide solution)
Result: White precipitate of calcium carbonate formed (solution turns milky)

Carbon dioxide is colourless and odourless.

Question 3

What’s the test and result for

Chlorine (Cl₂)

Answer 3

Test: Hold damp litmus paper (or Universal Indicator paper) in gas
Result: Indicator paper is bleached white (blue litmus will turn red first)

(This gas is poisonous, so test with care and use a fume cupboard.)

Chlorine is pale green with a choking smell.

Question 4

What’s the test and result for

Hydrogen (H₂)

Answer 4

Test: Hold a lighted splint in gas
Result: Hydrogen burns with a squeaky ‘pop’

Hydrogen is colourless and odourless.

Question 5

What’s the test and result for

Oxygen (O₂)

Answer 5

Test: Hold a glowing wooden splint in gas
Result: The splint re-lights

Oxygen is colourless and odourless.