C6 - Electroylsis - Complete

Question 1

What type of compound can be broken down by electrolysis?

Answer 1

An ionic compound

Question 2

What is the electrolyte of an electrolysis reaction?

Answer 2

The ionic compound being separated

Question 3

What is an electrode?

Answer 3

A conducting rod connected to a specific terminal from the power supply

Question 4

Which is the positive electrode?

Answer 4

The anode

Question 5

Which is the negative electrode?

Answer 5

The cathode

Question 6

What are the electrodes made of and why?

Answer 6

Unreactive substances such as graphite or platinum, so that they do not interfere with the separation process by reacting with the compound or separating themselves

Question 7

What happens during electrolysis?

Answer 7

The positive ions move to the negative and the inverse to the inverse, as opposite charges attract. At the electrodes, the ions lose their charges and become elements. Often a chemical will be deposited or a gas released, depending on the compound used and whether it was molten or dissolved in water

Question 8

Why are the compounds often dissolved in water or molten?

Answer 8

As when they are solid they cannot conduct electricity as their ions are fixed in a large lattice structure

Question 9

What does electrolysis do?

Answer 9

It breaks down a substance using electricity

Question 10

What is a setback of dissolving an ionic compound in water for electrolysis?

Answer 10

It can be hard to predict what will be formed at each of the electrodes, and in what form the products will be

Question 11

What happens when ions reach an electrode?

Answer 11

They either lose or gain electrons based on their charge

Question 12

What is the gaining of electrons called?

Answer 12

Reduction (Think OILRIG)

Question 13

What is the loss of electrons called?

Answer 13

Oxidation (Think OILRIG)

Question 14

What is the best way to display the reactions going on at each electrode?

Answer 14

Half equations that demonstrate the movements and charges of the particles (e.g. Pb + e- —> Pb-)

Question 15

What ions does water form when it ionises?

Answer 15

Hydrogen (H+) ions and Hydroxide (HO-) ions, both aqueous (aq)

Question 16

Out of more and less reactive ions, which is more likely to form at the electrode?

Answer 16

The less reactive one

Question 17

What is the order of most likely to be discharged at the anode to least likely?

Answer 17

Halide ions > Hydroxides > All other negatively charged ions

Question 18

What are 3 uses of aluminium or its alloys?

Answer 18

Pans / Overhead power cables / Aeroplanes / Cooking foil / Drink cans / Window and patio door frames / Bicycle frames and car bodies

Question 19

Why can’t aluminium be separated using any other method than electrolysis?

Answer 19

As it is too reactive to be displaced by carbon, is less reactive than magnesium but more so than iron and zinc

Question 20

What is the compound used to separate aluminium in electrolysis?

Answer 20

Al2O3

Question 21

What is the raw form of aluminium that can be extracted from the ground?

Answer 21

Bauxite ore, which is mainly aluminium, but also contains many rocky impurities such as Iron (III)

Question 22

Why is molten cryolite mixed with aluminium in electrolysis?

Answer 22

To lower aluminium’s high boiling point so that its extraction is more sustainable and consumes less energy

Question 23

Why do the carbon anodes used in aluminium purification have to be replaced?

Answer 23

As the oxygen that forms there often reacts with the carbon to make carbon dioxide: meaning that they end up wearing away over time

Question 24

What three useful products does the electrolysis of brine produce?

Answer 24

Chlorine gas at the anode, hydrogen gas at the cathode, and sodium hydroxide solution