C4.2

Question 1

How do you test for hydrogen?

Answer 1

Hold a lighted splint over the gas , a squeaky pop sound will be made

Question 2

Test for carbon dioxide

Answer 2

Limewater turns from colourless to cloudy.

Question 3

What is Limewater and it’s reaction to CO2

Answer 3

Calcium hydroxide solution + carbon dioxide = water + calcium carbonate (white precipitate)

Ca(OH)2 + CO2 = H2O + CaCO3(s)

Question 4

Chlorine test

Answer 4

(Dissolves in water to become acidic.)
Dampen blue litmus paper,
Should turn red and then white as it bleaches it

Question 5

Hydrogen test

Answer 5

Place a lit splint in gas, should make a squeaky pop sound

Question 6

Oxygen test

Answer 6

Glowing splint , should relit

Question 7

How do we see flame colours

Answer 7

As it burns, the metal ions are vaporised.
They absorb energy and the electrons jump to a higher electron shells (excited). As they come back down the energy is emitted off as radiation, visible light in the wave spectrum

Question 8

How do you conduct a flame test?

Answer 8

1. Clean Nichrome wire loop in HCL, hold it in the flame until it stops changing colour.
2. dip the loop into the test powder.
3. Hold it in the roaring flame and note the colour

Question 9

What colour is lithium

Answer 9

Red

Question 10

What colour is sodium

Answer 10

Yellow

Question 11

What colour is potassium

Answer 11

Lilac

Question 12

What colour is Calcium in the flame test?

Answer 12

Orange- Red

Question 13

What colour is copper

Answer 13

Green - blue

Question 14

What could be a source of error

Answer 14

Contamination

Question 15

Why is sodium hydroxide solution used in experiments?

Answer 15

Group 1 hydroxides are soluble in water.

Question 16

What is the hydroxide precipitate colour of Iron (ll)

Answer 16

Green

Question 17

What is the hydroxide precipitate colour of Iron (lll)

Answer 17

Orange - brown

Question 18

What is the hydroxide precipitate colour of copper(ll)

Answer 18

Blue

Question 19

What is the hydroxide precipitate colour of zinc

Answer 19

White however in excess the zinc hydroxide will dissolve into a colourless solution

Question 20

What is the reaction for the copper hydroxide test

Answer 20

CuSo4 (aq) + 2NaOH(aq) —> Cu(OH)2 (s) + Na2SO4 (aq)

Net ionic equation:
Cu 2+ (aq) + OH- (aq) —> cu(OH)2 (s)

Question 21

What is an anion

Answer 21

A negative ion

Question 22

What is a cation

Answer 22

A positive ion

Question 23

How to test for Sulfate ions (SO4 2-)?

Answer 23

1. Add HCL
2. Add barium chloride, BaCl2
3. A white precipitate (barium sulphate)forms if sulphate ions are present

Question 24

How do you test for carbonate ions?

Answer 24

1. Add some HCl to solution
2. If carbonate is present then there is bubbling (the release of carbon dioxide)

2H+ (aq) + CO3 2-(aq) —> CO2 (g) + H2O (l)

Question 25

How do you test for the halides

Answer 25

1.Add some nitric acids( removes other ions present)
2. Add a few drops of silver nitrate solution AgNO3 (aq)
Chlorine- white
Bromine- cream
Iodine- yellow

(MILK, CREAM , BUTTER)