Reactivity and Redox

Question 1

Reduction

Answer 1

Gain of Electrons

Or loss of oxygen

Question 2

Redox Reaction

Answer 2

When oxidation and reductions happen at the same time.

Question 3

Oxidising Agent

Answer 3

A chemical that accept electrons and gets reduced in a reaction.

Question 4

Reducing Agent

Answer 4

A chemical that donates electrons and gets oxidised in a reaction.

Question 5

Displacement Reaction

Answer 5

A reaction where a more reactive metal displaces a less reactive one from its compound.

Question 6

Reactivity Series

Answer 6

Potassium 
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Hydrogen
Copper
Silver
Gold

Question 7

Oxidation

Answer 7

Loss of Electrons

Or gain of oxygen

Question 8

Ore

Answer 8

A naturally-occurring material which contains a metal that can be extracted.

Question 9

Extraction

Answer 9

Removing a metal from its ore.

Question 10

Native Metal

Answer 10

A metal found in its metallic form or as an alloy in nature. E.g. Gold

Question 11

Haematite

Answer 11

• Iron ore
• Fe2O3
• Iron Oxide

Question 12

Bauxite

Answer 12

• Aluminium Ore
• Al2O3
• Aluminium Oxide

Question 13

Blast Furnace

Answer 13

Where the extraction of iron from its ore happens.

Question 14

Rust

Answer 14

• Hydrated Iron Oxide
• Fe2O3
• The product of the corrosion of iron

Question 15

Corrosion

Answer 15

Deterioration of a metal due to its surroundings, such as air and water.

Question 16

Sacrificial Protection

Answer 16

Coating a metal (often iron) with a more reactive one. This metal loses its electrons first and stops the metal underneath getting corroded.

Question 17

Galvanising

Answer 17

Coating a iron in zinc to

1) Work as sacrificial protection
2) Work as a physical barrier

Question 18

Electrolysis

Answer 18

The break down of an ionic substance that is molten or in a solution by passing electricity through it.

Question 19

Electrode

Answer 19

In electrolysis, for there to be a circuit, there has to be a:

• Anode - Positive electrode
• Cathode - Negative electrode

Question 20

Cryolite

Answer 20

Cryolite is a less common ore of aluminium in which aluminium oxide is dissolved in to lower the melting point for electrolysis.

Question 21

Ionic Half-Equation

Answer 21

These are used to show what is happening at each electrode during electrolysis.

Question 22

How are the reactions of metals with acid used to deduce the reactivity series?

Answer 22

The faster the reaction happens, the more reactive the metal is. This is the rate at which bubbles are produced and can be tested using a burning splint.

Acid + Metal -> Salt + Hydrogen

Question 23

How are the reactions of metals with water used to deduce the reactivity series?

Answer 23

• Potassium, Sodium, Lithium, Calcium = Vigourous reaction
• Magnesium, Zinc, Iron, etc. = Not very reactive unless with steam
• Copper = Not at all reactive

Question 24

How are displacement reactions used to deduce the reactivity series?

Answer 24

A more reactive metal always displaces a less reactive one.

Question 25

When are redox reactions used in the extraction of metals?

Answer 25

If a metal is less reactive than carbon, heating a metal oxide with carbon monoxide can allow the carbon monoxide reduce the metal oxide by 'stealing' the oxygen.

Question 26

How are metals extracted with regards to the reactivity series?

Answer 26

Above Carbon = Electrolysis | Below Carbon = Heating with Carbon Monoxide

Question 27

What are the 3 raw materials that are put into the blast furnace?

Answer 27

Iron Ore (Haematite) - Fe2O3 Coke (Carbon) - C Limestone - CaCO3

Question 28

What are the main reactions that happen in the blast furnace?

Answer 28

Reducing Iron Ore C + O2 -> CO2 CO2 + C -> 2CO 3CO + Fe2O3 -> 3CO2 + 2Fe Removing Impurities CaCO3 -> CaO + CO2 CaO + SiO2 -> CaSiO3

Question 29

What are the products of the blast furnace?

Answer 29

- Iron - Slag - Waste Gases

Question 30

What is needed for iron to rust?

Answer 30

Water and Oxygen (Air)

Question 31

What does each of the raw materials in the blast furnace do?

Answer 31

Iron Ore - Contains iron. Coke - Contains carbon which is used for reducing iron oxide. Limestone - Reacts with impurities to form slag.

Question 32

What are the different methods for preventing rusting?

Answer 32

``` Barrier - Painting / Coating with plastic - Oiling / Greasing Sacrificial Protection - Galvanising - Coating in more reactive metals than iron ```

Question 33

How is aluminium extracted?

Answer 33

1) Aluminium oxide is dissolved in molten cryolite 2) Molten aluminium oxide contains free ions: Al3+ and O2- 3) The positive aluminium ions are attracted to the negative cathode, gain electrons and become aluminium atoms. 4) The negative oxygen ions are attracted to the positive anode, lose electrons there and become oxygen atoms.

Question 34

Why and what is cryolite used for?

Answer 34

Aluminium oxide is dissolved in cryolite (a less common aluminium ore) before electrolysis due to the fact that it has a lower melting point (950*C), which saves energy.

Question 35

What is the half-equation for the reaction at the anode, during aluminium extraction?

Answer 35

2O2− → O2 + 4e−

Question 36

What is the half-equation for the reaction at the cathode, during aluminium extraction?

Answer 36

Al3+ + 3e− → Al

Question 37

Why does the anode (positive electrode) need to be replaced, during aluminium extraction?

Answer 37

It is made of carbon, which reacts with the oxygen produced there, making CO2, which causes it to get worn away.

Question 38

Why is aluminium extraction expensive?

Answer 38

- Requires lots of electricity - Requires energy to melt cryolite - Positive electrodes need replacing - Needs to be mined

Question 39

Uses of Iron

Answer 39

Wrought Iron (Almost pure iron) - Malleable -> Ornamental gates and railings Cast Iron (Iron, Carbon, Silicon) - Hard, but brittle -> Manhole covers and cooking pans Steel (Iron, Carbon, Some other metals) - Hard and malleable -> Car bodies and construction girders Stainless Steel (Iron, Chromium) - Doesn't rust -> Cutlery, Cooking pans

Question 40

Uses of Aluminium

Answer 40

- Doesn't corrode easily (forms a protective layer) -> Things that come in contact with water e.g. Drinks cans - Light -> Bicycle frames and aeroplanes

Question 41

What is the order of the reactivity series?

Answer 41

``` Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold Platinum ```

Question 42

What is a mnemonic for the reactivity series?

Answer 42

``` Please Send Cheetham's Mongoose A Cool Zebra. In The Library Hari Can't Study General Physics. ```