C2.5 Salts And Electrolysis

Question 1

What pH is neutral?

Answer 1

pH 7

Question 2

Give an example of an acid at pH 1

Answer 2

Battery acid

Question 3

Give an example of an alkali at pH 14

Answer 3

Bleach

Oven cleaner

Question 4

What two methods test for pH? What’s more useful?

Answer 4

Universal indicator
Litmus paper
Universal indicator is more useful because it shows you a specific colour so you can tell whether it’s a weak or strong acid/alkali

Question 5

What’s an ion?

Answer 5

A charged particle

Question 6

Fill in the gaps:
When metal atoms lose electrons, they form ________ ions.
When non-metal atoms gain electrons they form ________ ions.

Answer 6

1. Positive

2. Negative

Question 7

What’s an acid?

Answer 7

Somethings that forms H+ ions when added to water

Question 8

What’s an alkali?

Answer 8

It forms hydroxide ions, OH- , when added to water

Question 9

What’s a base?

Answer 9

Anything that neutralises acids but can’t dissolve in water

Question 10

What’s the difference between an alkali and a bass?

Answer 10

They both neutralise acids but bases can’t dissolve in water whereas alkalis can.

Question 11

What does ‘aq’ mean?

Answer 11

A solution - something dissolved in water

Question 12

Copper oxide + sulphuric acid ->

Answer 12

Copper sulphate + water

Question 13

Acid + alkali (base) ->

Answer 13

Salt + water

Question 14

Acid + metal ->

Answer 14

Salt + hydrogen

Question 15

Acid + metal carbonate ->

Answer 15

Salt + water + carbon dioxide

Question 16

Hydrochloric acid + copper ->

Answer 16

Copper chloride + hydrogen

Question 17

Calcium carbonate + sulphuric acid ->

Answer 17

Calcium sulphate + water + carbon dioxide

Question 18

What happens when two soluble salts are reacted together?

Answer 18

Makes an insoluble salt

Question 19

What’s the ionic equation for neutralisation?

Answer 19

H+(aq) + OH-(aq) -> H2O(l)

Acid + alkali -> water

Question 20

Define electricity (in chemistry terms)

Answer 20

Flow of charge

Question 21

Define electrolysis

Answer 21

Using electricity to separate ionic compounds

Question 22

What ions are attracted to the cathode?

What ions are attracted to the anode?

Answer 22

1. Positive

2. Negative

Question 23

When you use electrolysis to separate copper chloride what would you see at the positive electrode? Negative electrode?

Answer 23

Positive electrode- bubbles of green/yellow gas (chlorine)

Negative electrode- copper coloured solid

Question 24

What’s the name of the negative electrode?

Answer 24

Cathode

Question 25

What's the name of the positive electrode?

Answer 25

Anode

Question 26

Positive ions are _______ - they ______ electrons | Negative ions are ______ - they _____ electrons

Answer 26

Reduced Gain Oxidised Lose

Question 27

What does OILRIG stand for 😌

Answer 27

Oxidation Is Loss (of electrons) | Reduction Is Gain (of electrons)

Question 28

What's the half equation for sodium chloride (NaCl)

Answer 28

Na+ + e- -> Na | 2Cl- -> Cl2 + 2e-

Question 29

What are the products when you electrolyse brine? | What do we use them for?

Answer 29

Chlorine - swimming pools Hydrogen - fuels Sodium hydroxide - cleaning substances

Question 30

What is brine?

Answer 30

Salt water | Sodium chloride dissolved in water

Question 31

When you look for the products of electrolysis what products come first on the cathode?

Answer 31

``` Metals below hydrogen Then Hydrogen Then Metals above hydrogen ```

Question 32

When you look for products of electrolysis what comes first on the anode?

Answer 32

``` Halogens (group 7) Then Hydroxide (oxygen) Then All other negative ions ```

Question 33

When you electrolysis of copper sulphate what do you see at the negative electrode? Why?

Answer 33

Copper is attracted to the cathode because copper ions are positive so they're attracted to the negative electrode as opposites attract. The copper ions become neutral which form atoms as the copper gained two electrons. Copper ions are reduced and it becomes an atom which means it becomes solid

Question 34

When you use electrolysis to separate copper sulphate what do you see at the positive electrode? Why?

Answer 34

The anode generates bubble around it and produces oxygen because the hydroxide which are negative to the positive electrode. It's oxidised as it loses electrons and it becomes neutral meaning oxygen is produced which evaporates meaning bubbles are formed

Question 35

What happens during electroplating?

Answer 35

The negative electrode is the object that is to be electroplated The positive electrode is the metal you want to coat the object with The electrolyte should be a solution of the coating metal such as its metal nitrate or sulphate

Question 36

How do you plate a metal spoon in silver?

Answer 36

The metal spoon is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution. The spoon is then coated in silver.

Question 37

Why is electroplating useful?

Answer 37

Gives the object a protective layer - resistant to corrosion Looks nicer (jewellery) Cheaper to coat an object in gold/silver than the whole object being made of the metal

Question 38

When we extract aluminium, why does aluminium oxide have to be molten?

Answer 38

So the ions can move freely and separate easily to the electrodes

Question 39

Why is cryolite added when we extract aluminium?

Answer 39

To lower the melting point - less energy uses - cheaper

Question 40

When you extract aluminium why do you have to regularly replace the carbon anodes?

Answer 40

They react with the oxygen and create carbon dioxide which wears the anodes away

Question 41

What are the half equations for aluminium oxide (Al2O3)?

Answer 41

Al3+ +3e- -> Al 2O2- -> O2 + 4e-