Tests for gasses

How to collect gas

How to collect gas

How to measure amount of gas produced

Use a gas syringe (this is the most efficient method)

Test for Carbon Dioxide (CO₂)?

Add calcium carbonate to some hydrochloric acid and add in the substance you are testing

Attach a bung and delivery tube to the test tube and put the tube into a test tube of limewater, bubbles should start to come through the tube into the limewater

If CO₂ is present the limewater will turn milky/cloudy in colour

Why does limewater go cloudy in the presence of carbon dioxide?

Because a reaction is occuring

Test for chlorine

Dip damp blue litmus paper in the chlorine gas, it will turn red (because chlorine is acidic) then white (because the chlorine acts as a bleach)

The gas will also be a green-yellow colour and smell like a swimming pool, but the test above is used to confirm this

Test for oxygen

Fill a test tube with peroxide

Add yeast and wait for it to dissolve

Keep your thumb or a bung on the top to stop the gas from escaping

Add a glowing splint (not on fire but as if you blew out a candle and its the hot orang part left) into the test tube

If the splint re-lights then oxygen is present (because flames need oxygen)a

How to get hydrogen?

Mix a metal (e.g. magnesium) with an acid (e.g. hydrochloric acid) and collect the gas

because a metal + acid = Salt + water + Hydrogen Gas

Test for hydrogen

The squeaky pop test:

Fill a test tube with hydrochloric acid

Add magnesium and wait for it to dissolve

Add a light splint to the test tube

If you hear a squeaky pop, the hydrogen is present

Unknown gas, what order would you test it? (Bonus question)

Test for ammonia

Dip damp red litmus paper into the gas

If it turns blue then it is ammonia

Test for sulfer dioxide?

Add to acidified aqueous potassium manganate (VII)

It will turn from purple to colourless