Redox, Rusting And Iron

Question 1

What is Reduction? (3)

Answer 1

A reaction in which a substance either:

• gains electrons
• gains hydrogen
• loses oxygen

Question 2

What is Oxidation? (3)

Answer 2

A reaction in which a substance either:

• loses electrons
• loses hydrogen
• gains oxygen

Question 3

What is a redox reaction? (3)

Answer 3

• When oxidation and reduction occur
• at the same time
• in the same reaction

Question 4

What is the chemical name and formula for rust?

Also, what is its appearance?

Answer 4

• Hydrated Iron (III) Oxide
• Fe₂O₃ . XH₂O
• flakey orange-brown solid

Question 5

What conditions are needed for rusting to occur? (2)

Answer 5

• water
• oxygen

Question 6

What apparatus can be used to demonstrate the conditions for rusting in Iron?

Answer 6

• one test tube with:
  1. O₂ present.
  2. Anhydrous Calcium Chloride to absorb water
  3. Dried air
  No rusting will occur
• another test tube with:
  1. H₂O and O₂ present
  2. distilled water
  3. air
  Rusting will occur
• another test tube with:
  1. Only H₂O present
  2. A layer of oil
  3. Boiled water
  No rusting will occur

Question 7

What methods can be used to prevent rusting?

Answer 7

• plastic coating
• painting
• oiling
• galvanising
• sacrificial protection

Question 8

How is sacrificial protection used to prevent rusting of Iron? (2)

Answer 8

• water and oxygen reacts with a more reactive metal e.g. Zinc
• this coats the Iron

Question 9

What is the common name for iron ore?

Answer 9

Haematite

Question 10

What raw materials are used in a blast furnace?

Answer 10

1. Haemitite
   - Iron (III) Oxide = chemical name
   - Fe₂O₃ = Formula
2. Coke
   - Carbon = chemical name
   - C = Formula
3. limestone
   - Calcium Carbonate = chemical name
   - CaCO₃

Question 11

In a blast furnace, how is the reducing agent made?

Answer 11

Hot air is blasted into the furnace:
- the oxygen reacts with he coke (carbon) to form CO₂ (carbon dioxide
- the carbon dioxide reacts with the coke (carbon) to form CO (carbon monoxide)

Equations:
- O₂ + C —> CO₂
- CO₂ + C —> 2CO

Question 12

How is haemitite (Iron (III) Oxide) reduced to form Iron?

What type of reaction is this?

Answer 12

3CO + Fe₂O₃ —> 2Fe +3CO₂

(Carbon monoxide acts as the reducing agent)

Redox reaction: Oxygen lost by Iron (reduction), gained by Carbon Monoxide (oxidation)

Question 13

Explain the reactions involved in removing acidic impurities in a blast furnace.

Answer 13

1. Thermal decomposition of Calcium Carbonate (Limestone)
   HEAT
   - CaCO₃ —> CO₂ + CaO
2. Calcium Oxide + Silicon Dioxide —> Calcium Silicate (Slag)
   - CaO + SiO₂ —>CaSiO₃

Question 14

How are Iron and Slag removed in a blast furnace?

Answer 14

• Both are in molten form
• Iron is more dense than Slag
• Slag floats above Iron, both can be tapped off

Question 15

What is the pneumonic for remembering how oxidation and reduction occur (electrons and hydrogen only)

Answer 15

Oxidation
Is
Loss
Reduction
Is
Gain

Question 16

Describe Phytomining (4)

Answer 16

• Plants absorb metal compounds (e.g. Copper salts)
• The plants are harvested, then burned to produce ash, which contains the metal compounds;
• Acid (generally sulfuric acid) is reacted with the ash to produce a solution containing dissolved metal compounds (leachate);
• Metals can be obtained from these solutions by displacement with scrap iron and

Question 17

What are the 3 main advantages of pytomining?

Answer 17

• Avoids noise and dust pollution
• Produces energy when plants are burned
• Uses no energy transporting any rocks

Question 18

What are the 2 main disadvantages of pytomining?

Answer 18

• It is a very slow process
• It is seasonal

Question 19

What are the observations for the reaction between iron and copper sulphate? (2)

Answer 19

• blue solution fades
• red-brown solid deposited