C14: Electrolysis

Question 1

Electrolyte

Answer 1

A liquid containing free moving ions that is broken down by electricity during the process of electrolysis.

Question 2

Electrolysis

Answer 2

The breakdown of a substance containing ions by electricity.

Question 3

The positive electrode

Answer 3

Anode

Question 4

The negative electrode

Answer 4

Cathode

Question 5

What sort of compounds are usually electrolysed?

Answer 5

Ionic compounds.

Covalent compounds can only do it if they react in the water to form ions.

Question 6

Equation at the anode

Answer 6

n- -> n + e-

Question 7

Equation at the cathode

Answer 7

n+ + e- -> n

Question 8

Will the more or less reactive element be formed at the cathode?

Answer 8

Less reactive

Question 9

What is the ‘order of discharge’ at the anode?

Answer 9

Halide ion > Hydroxide > All other negatively charged ions.

Question 10

What gas is often given off at the anode?

Answer 10

Oxygen

Question 11

Name of aluminium ore

Answer 11

Bauxite

Question 12

What substance is mixed with aluminium during electrolysis and why?

Answer 12

Molten cryolite

It reduces the melting point

Question 13

What happens at the cathode during the electrolysis of aluminium?

Answer 13

Al3+ ions are reduced to form Al atoms.

This forms aluminium at the bottom of the tank and is then siphoned off.

Question 14

What happens at the anodes during the electrolysis of aluminium?

Answer 14

O2- ions turn into oxygen atoms.
These bond in pairs to form oxygen gas.
The oxygen reacts with the carbon anodes, forming Carbon Dioxide.
Due to the this the anodes must be replaced regularly.

Question 15

What three products are formed in the electrolysis of brine and where?

Answer 15

> Chlorine gas- anode
Hydrogen gas- cathode
Sodium Hydroxide solution

Question 16

How is brine electrolysed in industry?

Answer 16

Using a diaphragm cell, where the two electrodes are separated by a porous membrane.

Question 17

Why is sodium hydroxide produced in the electrolysis of brine?

Answer 17

During the electrolysis of brine, Na+, Cl-, H+ and OH- are present. Chlorine and Hydrogen gas are emitted during the electrolysis process, which leaves only sodium and hydroxide.

Question 18

2 uses of chlorine.

Answer 18

> When reacted with sodium hydroxide it can be used as bleach.
Plastics such as PVC

Question 19

Use for hydrogen

Answer 19

> Makes margarine when combined with veritable oils.

Question 20

Use for sodium hydroxide

Answer 20

> Important alkali in industry
Bleach
Soap
Paper

Question 21

Electroplating

Answer 21

The process of depositing a thin layer of metal onto an object during electrolysis.

Question 22

Why do we electroplate objects?

Answer 22

> To protect the metal beneath from corrosion.
To make the object look more attractive.
To increase the hardness or resistance to scratching.
To save money.

Question 23

In electroplating, what substances make up the anode and cathode?

Answer 23

> Cathode- Object to be electroplated

> Anode - Metal to plate the Object.