Chemical Testing

Question 1

chlorine gas

Answer 1

• damp blue litmus paper
• turns red, then bleaches white
• wear a gas mask, do experiment in fume cupboard

Question 2

oxygen gas

Answer 2

• glowing splint

- relights

Question 3

hydrogen gas

Answer 3

• lit splint

- squeaky pop

Question 4

carbon dioxide gas

Answer 4

• bubble through limewater

- turns cloudy

Question 5

carbonate anions

Answer 5

• react substance w hydrochloric acid
• if carbonate ions present, CO2 will bubble out of solution
• bubble through limewater
• if it’s cloudy, CO2 is present, so ion is a carbonate

Question 6

• sulfate anions

Answer 6

• react substance with hydrochloric acid
• add barium chloride solution
• if sulphate ions are present, a white precipitate of barium sulfate will form

Question 7

halide anions

Answer 7

• react solution with nitric acid to remove carbonate or sulfite ions
• add silver nitrate
• white precipitate = chloride
• cream precipitate = bromide
• yellow precipitate = iodide

Question 8

lithium cation flame test

Answer 8

• dip platinum/nichrome wire loop in HCL, then heat over Bunsen burner
• dip wire loop into lithium
• hold it in blue part of flame (hottest)
• turns crimson

Question 9

sodium cation flame test

Answer 9

• dip platinum/nichrome wire loop in HCL, then heat over bunsen burner
• dip wire loop into sodium
• hold in blue part of flame (hottest)
• turns yellow

Question 10

potassium cation flame test

Answer 10

• dip platinum/nichrome wire loop in HCL, then heat over Bunsen burner
• dip wire into potassium
• hold it in blue part of the flame (hottest)
• turns lilac

Question 11

calcium cation flame test

Answer 11

• dip platinum/nichrome wire in HCL, then heat over Bunsen burner
• dip wire loop into calcium
• hold it in blue part of the flame(hottest)
• turns orange/red

Question 12

copper cation flame test

Answer 12

• dip platinum/nichrome wire loop in HCL, then heat over bunsen burner
• dip wire loop into copper
• hold it in blue part of flame (hottest)
• turns green

Question 13

copper (II) metal hydroxide cation

Answer 13

• react it with sodium hydroxide

- forms a blue precipitate

Question 14

calcium metal hydroxide cation

Answer 14

• react it with sodium hydroxide

- forms a white precipitate

Question 15

iron (II) metal hydroxide cation

Answer 15

• react it with sodium hydroxide

- forms a green precipitate

Question 16

iron (III) metal hydroxide cation

Answer 16

• react it with sodium hydroxide

- forms a brown precipitate

Question 17

magnesium metal hydroxide cation

Answer 17

• react it with sodium hydroxide

- forms a white precipitate

Question 18

aluminium metal hydroxide cation

Answer 18

• react it with sodium hydroxide
• forms a white precipitate
• unless in excess, then becomes colourless