Gas Tests

Question 1

how do we test for hydrogen?

Answer 1

squeaky pop test:

1. collect a sample of gas in a test tube
2. attempt to ignite the gas using a lit splint

result = squeaky pop sound

Question 2

what causes the squeaky pop sound in the hydrogen test?

Answer 2

the hot gas rushing out of the test tube

Question 3

how do we test for oxygen?

Answer 3

glowing splint test:

1. collect a sample of gas in a test tube
2. place a glowing splint into the tube

result = the splint relights

Question 4

why does the splint relight in the oxygen test?

Answer 4

because pure oxygen is more concentrated than the oxygen in normal air - this means the wood in the splint combusts faster

Question 5

how do we test for the presence of water?

Answer 5

copper sulfate test:

1. add anhydrous copper sulfate

result = it changes colour from white to blue

Question 6

how to test for the purity of water?

Answer 6

1. measure its boiling point
2. compare it to 100 degrees C

result = closer to 100 degrees C means it is more pure

Question 7

how do we test for carbon dioxide?

Answer 7

the limewater test:

1. bubble a sample of gas through limewater

result = a white precipitate forms (turns cloudy)

Question 8

how do we test for chlorine?

Answer 8

the damp blue litmus test:

1. place damp blue litmus paper in a sample of gas

result = it turns white (bleaches)

Question 9

how does the chlorine test work?

Answer 9

chlorine is a good bleaching agent, so it easily removes colour from other substances - in this test it dissolves into the dampness and removes the colour from the blue litmus

Question 10

how do we test for ammonia?

Answer 10

the damp red litmus test:

1. place damp red litmus paper in a sample of gas

result = it turns blue

Question 11

how does the ammonia test work?

Answer 11

• ammonia reacts with the dampness to form OH- ions
• the ammonia acts as a base by accepting H+ ions from the water
• the OH- ions are what’s left and they are alkaline so the litmus turns blue