Testing Gases: Hydrogen, Oxygen, Carbon Dioxide, and Chlorine

This lesson covers methods to test for the presence of hydrogen, oxygen, carbon dioxide, ammonia, and chlorine gases in the laboratory. Each gas has distinct testing methods: hydrogen produces a squeaky pop with a lit splint, oxygen relights a glowing splint, carbon dioxide turns lime water milky, ammonia turns damp red litmus paper blue and forms ammonium chloride smoke, and chlorine turns damp blue litmus paper red and bleaches it. These tests help identify gases that are otherwise indistinguishable by appearance.

Why is it difficult to identify gases just by their appearance?

• They have distinct smells.

• They have different colors.

• They are all visible.

• They are all colorless and odorless.

What sound confirms the presence of hydrogen when tested with a lit splint?

• A loud bang

• No sound

• A squeaky pop

• A hissing sound

What happens to a glowing splint in the presence of oxygen?

• It extinguishes.

• It relights.

• It makes a popping sound.

• It changes color.

Why does hydrogen produce a squeaky pop sound?

• It absorbs oxygen.

• It reacts with carbon dioxide.

• It is not flammable.

• It is highly flammable and causes a mini explosion.

What is the concentration of oxygen in air?

• 75%

• 10%

• 21%

• 50%

What happens to lime water in the presence of carbon dioxide?

• It turns clear.

• It remains unchanged.

• It turns milky.

• It changes to blue.

What color does damp red litmus paper turn in the presence of ammonia?

• Yellow

• Red

• Blue

• Green

What compound forms when ammonia reacts with concentrated hydrochloric acid?

• Calcium carbonate

• Ammonium chloride

• Sodium chloride

• Calcium hydroxide

What happens to damp blue litmus paper in the presence of chlorine?

• It turns yellow.

• It remains blue.

• It turns red and then white.

• It turns green.

Which gas turns lime water milky?

• Ammonia

• Carbon dioxide

• Oxygen

• Hydrogen