CHEMICAL TESTS

Question 1

Test for HYDROGEN

Answer 1

METHOD: collect gas into boiling tube and place a lit splint inside
POSITIVE RESULT: there´s a squeaky pop if H+ is present

Question 2

Test for OXYGEN

Answer 2

METHOD: collect gas into boiling tube and insert glowing splint
POSITIVE RESULT: splint relights if oxygen is present

Question 3

Test for CO2

Answer 3

METHOD: boil gas through limewater and observe the colour change
POSITIE RESULT: limewater turns milky/cloudy if CO2 is present

Question 4

Test for AMMONIA

Answer 4

METHOD: put damp red litmus paper or universal indicator paper into test solution
POSITIVE RESULT: Red litmus paper turns blue if ammonia is present.
- Universal indicator paper turns purple if ammonia is present.

Question 5

Test for CHLORINE

Answer 5

METHOD: put damp litmus paper/ starch-iodide paper into test solution.
POSITIVE RESULT: Damp litmus paper bleached white if chlorine is present.
- Starch-iodine paper turns blue if chlorine is present.

Question 6

How do you carry out a flame test?

Answer 6

1. Dip platinum or nichrome wire into concentrated hydrochloric acid + then in salt you want to test
2. Wire + salt held on top of bunsen burner + colour is observed

Question 7

What flame colour does K+ produce?

Answer 7

Lilac

Question 8

What flame colour does Ca2+ produce?

Answer 8

Orange-red

Question 9

What flame colour does Li+ produce?

Answer 9

Red

Question 10

What flame colour does Na+ produce?

Answer 10

Yellow

Question 11

What flame colour does Cu2+ produce?

Answer 11

Blue-green

Question 12

What precipitate colour does Copper turn?

Answer 12

When sodium hydroxide is added, turns BLUE

Question 13

What precipitate colour does Iron II turn?

Answer 13

When sodium hydroxide is added, turns GREEN

Question 14

What precipitate colour does Iron III turn?

Answer 14

When sodium hydroxide is added, turns BROWN

Question 15

Test for anions CL-, Br- and I-

Answer 15

METHOD: add nitric acid followed by silver nitrate solution
POSITIVE RESULTS:
- Cl- turns white if chloride ions are present
- Br- turns cream if bromide ions are present
- I- ions turn yllow if iodide ions are present

Question 16

Test for SO4(2-)

Answer 16

METHOD:
Add dilute hydochloric acid to remove carbonate ions + add barium chloride solution
POSITIVE RESULTS: white precipitate formed (barium sulfate)

Question 17

Test for CO3(2-)

Answer 17

METHOD: Add dilute hydrochloric acid + bubble gas produced through limewater
POSITIVE RESULT: carbon dioxide formed if carbonate ions are present. (CO2 makes limewater milky)

Question 18

Test for WATER

Answer 18

METHOD: add liquid to anhydrous copper (ii) sulfate

POSITIVE RESULT: anhydrous copper (ii) sulfate turns blue is water is present

Question 19

Test for WATER PURITY

Answer 19

METHOD: measure freezing, melting or boiling point
POSITIVE RESULT: pure water freezes at 0C and boils at 100C
If water is impure, it will boil at higher temp + freeze at lower temp.