Gas identification and Flame Tests

What is the test for oxygen?

1. Place a glowing splint in a test tube of gas

2. If the splint relights, the gas is oxygen

What is the test for hydrogen?

1. Place a lit splint in a test tube of gas

2. If a squeaky pop sound is heard, the gas is hydrogen

What is the test for carbon dioxide?

1. Bubble the suspected gas through limewater

2. Limewater turns from colourless to cloudy in the presence of carbon dioxide

What is the test for chlorine?

1. Place damp blue litmus paper in a test tube of gas

2. If the litmus paper turns red and then bleaches, the gas is chlorine

What is the test for ammonia?

1. Place damp red paper in a test tube of gas

2. If the litmus paper turns blue, the gas is ammonia

What are the tests for water?

1. Dip cobalt chloride paper into a liquid. If the paper turns from blue to pink, the liquid is water

2. Anhydrous copper sulphate turns from white to blue in the presence of water

What is the test for an alkene?

1. Bromine water turns from red-orange to colourless in the presence of an alkene

How do you perform a flame test?

1. Dip the nichrome wire into hydrochloric acid

2. Flame the wire over a bunsen burner until it is clean

How do you do the flame test for sodium?

1. Dip the nichrome wire into hydrochloric acid, and flame the wire over the bunsen burner until it's clean

2. Dip the wire into a compound, and hold over the bunsen burner. If the flame turns yellow, the compound contains sodium

How do you do the flame test for potassium?

1. Dip the nichrome wire in hydrochloric acid, and flame over the bunsen burner until it's clean

2. Dip the wire into a compound, and then hold over the bunsen burner. If the flame turns lilac the compound contains potassium.

How do you do the flame test for lithium?

1. Dip nichrome wire into hydrochloric acid, and flame the wire over the bunsen burner until its clean

2. Dip the wire into a compound, and then hold over the bunsen burner. If the flame turns crimson red, the compound contains lithium

How do you do the flame test for calcium?

1. Dip nichrome wire in hydrochloric acid, and then flame the wire over a bunsen burner until it's clean

2. Dip the wire into a compound, and then hold over the bunsen burner. If the flame turns brick red, the compound contains calcium

How do you do the flame test for copper?

1. Dip nichrome wire into hydrochloric acid, and then flame the wire over a bunsen burner until it's clean

2. Dip the wire into a compound, and then hold over the bunsen burner. If the flame turns blue-green, the compound contains copper

How do you ensure that the nichrome wire is clean?

Hold the nichrome wire over the flame. If the flame shows no colour change to the colour of the original flame, the nichrome wire is clean

What wire can replace nichrome wire?

1. Platinum wire

Suggest why the litmus paper used to test for ammonia gas has to be damp.

1. So that the ammonia can react with/dissolve

in the water

2. So a colour change can be seen

3. So hydroxide ions form

Name the precipitate that makes the limewater cloudy.

Calcium carbonate