Extracting Metals

Question 1

Electrolysis definition

Answer 1

Breaking down of a substance using a direct current

Question 2

What is oxidation ?

Answer 2

Loss of electrons

Question 3

What is reduction?

Answer 3

Gain of elecrrons

Question 4

What happens at the anode?

Answer 4

Positive cations are attracted and are reduced (gains electrons)
Creates a flow of charge through electrolyte to complete the
circuit
Product is then discharged from electrolyte

Question 5

What happens at the anode?

Answer 5

Negative anions are attracted and are oxidised (lose electrons)
Creates a flow of charge through electrolyte to complete the circuit
Product is then discharged from electrolyte

Question 6

Half equation of sodium at cathode

Answer 6

Na -> Na+ + e-

Question 7

Half equation of hydrogen at anode

Answer 7

2H+ + 2e- -> H2

Question 8

Product at cathode in aqueous solution

Answer 8

If hydrogen and metal ions are present, if metal is more reactive than hydrogen, hydrogen will be produced

Question 9

Product at anode in aqueous solution

Answer 9

If hydroxide and halide ions were present, halogens would be formed. If no halide ions, oxygen would be formed

Question 10

What happens to copper electrodes im electrolysis?

Answer 10

Copper anodes lose mass Cu(s) -> Cu2+ (aq) + 2e-

Copper cathodes gain mass (copper from anode) Cu2+ 2e- -> Cu(s)

Question 11

What happens in electrolysis of impure copper?

Answer 11

Impure copper anode is oxidised, dissolving into electrolyte to form copper ions
Copper ions are reduced at pure copper cathode and forms pure copper layer
Any impurities from impure copper anode form a sludge at bottom of cell

Question 12

Reactivity series mnemonic

Answer 12

Pop - Potassium (K)
Stars - Sodium (Na)
Can - Calcium (Ca)
Make - Magnesium (Mg)
Absolute  - Aluminium (Al)
Crazy - Carbon (C)
Zillions - Zinc (Zn)
If - Iron (Fe)
Tiny - Tin (Sn)
Little - Lead (Pb)
Huge - Hydrogen (H)
Children - Copper (Cu)
Spend - Silver (Ag)
Gold - Gold (Au)
Pennies - Platinum (Pt)

Question 13

Reactivity in comparison to oxidation

Answer 13

More reactivity = more likely to oxidise and more likely to become ion
Less reactivity = less likely to oxidise and less likely to become ion

Question 14

Metal + water reaction

Answer 14

Metal + water -> metal hydroxide + hydrogen

Question 15

Speed of reaction to reactivity

Answer 15

Higher reactivity = faster rate of reaction

Question 16

How to choose metal extraction method

Answer 16

If more reactive than carbon, use electrolysis

If less reactive than carbon, heat with carbon unless inert

Question 17

Ore definition

Answer 17

Rock contains enough metal to be economically worthwhile to extract metal from

Question 18

Bioleaching method

Answer 18

Bacteria gets energy from bonds between atoms in ore, separating out metal from ore in process
Leachate (solution produced by process) contains metal ions which can be extracted using electrolysis or displacement

Question 19

Phytoextraction method

Answer 19

Plant grows in soil rich in metal compounds
Plant can’t use metal compounds so it gradually builds up in the leaves
Plants are harvested, dried and burned in a furnace
Metal compounds in ash can be extracted using electrolysis or displacement

Question 20

Recycling benefits

Answer 20

Doesn’t require combustion of fossil fuels (less energy, conserves finite resources e.g. metal)
Cuts down on amount of rubbish sent to landfills 
Saves money (less energy used in extraction, reuses metals harder to extract / buy, creates jobs)

Question 21

Life cycle

Answer 21

Choice of material
Manufacture
Product use
Disposal

Question 22

Choice of material in life cycle facts

Answer 22

Metals have to be mined and extracted, using energy and creating pollution
Raw materials for chemical manufacture come from crude oil and is non-renewable, requires lot of energy, generates pollution

Question 23

Manufacture in life cycle facts

Answer 23

Manufacturing uses energy and other resources
Creates pollution and waste which you need to dispose of safely
Chemical manufacture often needs water, and has a risk of polluting natural water sources

Question 24

Product use in life cycle facts

Answer 24

Using products can damage environment e.g.

• paint gives off toxic fumes
• burning fuels releases greenhouse gases
• fertilisers can leech into streams and rivers, damaging ecosystems

Question 25

Disposal in life cycle facts

Answer 25

Products are often disposed of in a landfill
Takes up space and can pollute land and water
Products may be incinerated, which causes air pollution