Chemical Tests

Question 1

What are the 3 gas tests?

Answer 1

hydrogen: pop test
oxygen: ignite/flame test
carbon dioxide: limewater test

Question 2

How do you test for hydrogen?

Answer 2

you take a lit split (flame) and touch it to the top/opening of a test tube fill with gas. if the the gas in the test tube contained hydrogen a pop sound will occur. if not, then the gas doesn’t contain any hydrogen.

Question 3

How do you test for oxygen?

Answer 3

oxygen supports combustion, so if you take a lit splint (flame) and touch it to the top of a test tube filled with the gas, if it relights with a flame then oxygen is present in the gas.

Question 4

How do you test for carbon dioxide?

Answer 4

carbon dioxide reacts with limewater forming white precipitate. so pass the gas through a container of limewater and if it turns cloudy white then carbon dioxide is present.

Question 5

What is limewater?

Answer 5

a solution of calcium hydroxide (CaOH)

Question 6

What are the flame tests for?

Answer 6

to test for cations and anions

Question 7

Describe the process of a flame test

Answer 7

1. dip wire loop in HCl and heat it in the flame until no colour appears to clean it
2. dip wire loop in the substance and then into the flame
3. observe the colour of the flame

Question 8

What are the colours of the flame test and what do they mean?

Answer 8

red = Li+
yellow = Na+
lilac = K+
orange = Ca2+
blue/green = Cu2+