2g (Testing for ions and gases)

Question 1

Test for oxygen

Answer 1

Glowing splint relights

Question 2

Test for hydrogen

Answer 2

Lit splint goes out with a squeaky pop

Question 3

Test for Carbon Dioxode

Answer 3

Lime water turns milky / cloudy

Question 4

Test for ammonia (NH3)

Answer 4

Damp red litmus paper turns blue

Question 5

Test for chlorine

Answer 5

Damp blue litmus paper bleaches/turns white

Question 6

Name of negative ions

Answer 6

anions

Question 7

Name of positive ions

Answer 7

cations

Question 8

Sulphate (NH42-)

Answer 8

-Add a few drops of hydrochloric acid (HCl)
-Add a few drops of barium chloride (BaCl2)

Result: white ppt.

Question 9

Halide ions (Cl, Br, I)

Answer 9

-Add a few drops of nitric acid (HNO3)
-Add a few drops of silver I nitrate (AgNO3)

Result: Cl- white ppt, Br- Cream ppt, I- yellow ppt

Question 10

Carbonate (CO32-)

Answer 10

-Put some acid (HCl) into a boiling tube with a side arm
-Add a spatula of material to be tested
-Bubble any gas into lime water

Result: If it is a carbonate, lime water will change from colourless to cloudy

Question 11

Metal ions (Cu2+, Fe2+, Fe3+)

Answer 11

-Put a small amount of solution in a test tube
-Add a few drops of sodium hydroxide (NaOH)

Result: Cu2+-blue solid ppt, Fe2+- green ppt, Fe3+-orange/brown ppt

Question 12

Flame test

Answer 12

-Clean a nichrome or platinum wire loop by dipping it in concentrated HCl and heat it in roaring flame
-Pick up some of the solid powder that you want to test
-Put the wire loop with the powder into the non-luminous part of the Bunsen flame

Question 13

Result flame test (Li+, Na+, K+, Ca2+, Cu2+)

Answer 13

Li+ - red
Na+ - orange
K+ - lilac
Ca 2+ - orange/red (brick red)
Cu2+ - Blue / green