2.3 Metals and Their Extractions

Where are metals located on the periodic table?

Left side of the 'staircase'.

List some properties of metals.

1. Good conductors of heat and electricity
2. Malleable and ductile
3. High melting and boiling points
4. High densities

What is metal extraction?

- Metals are extracted from ores which are rocks containing metal compounds found in the Earth's crust.
- The metals can be extracted using chemical reactions.

Reactivity series for metals.

Potassium- Most reactive
Sodium
Calcium
Magnesium
Aluminium
Carbon (used for comparison)
Zinc
Iron
Tin
Lead
Hydrogen (used for comparison)
Copper
Silver
Gold
Platinum- Least reactive

What mnemonic is used to remember the reactivity series for metals?

Please Send Cats, Monkeys And Cute Zebras In Their Lovely Happy Cages.

What is the relationship between metal reactivity and extraction?

The more reactive a metal is, the more stable its metal compound so the harder it is to extract the pure metal - i.e. gold is very unreactive so found in its pure form.

What are the extraction processes depending on the reactivity of a metal?

- Electrolysis - for metals more reactive than carbon
- Reduction with carbon - for metals less reactive than carbon (this is a cheap process and is favoured over electrolysis)
- Metals less reactive than hydrogen are found pure in their native form.

What is meant when a metal is found 'native'?

Found in its pure form as it is very unreactive.

What is a displacement reaction and how is it useful?

- When a more reactive metal displaces a less reactive metal from a compound
- AB+C-\>AC+B
- Can be used to investigate the relative reactivities of metals

What is oxidation?

Oxidation is the gain of oxygen or the loss of electrons.
It is also the loss of hydrogen.
The species oxidised is known as the reducing agent

What is reduction?

Reduction is the loss of oxygen or the gain of electrons.
It is also the gain of hydrogen.
The species oxidised is known as the reducing agent.

What mnemonic can be used to remember oxidation / reduction in terms of electrons?

OIL RIG
Oxidation is loss, Reduction is gain.

Which 3 forms can carbon be used as?

1. Charcoal
2. Coke
3. Wood

Which method do we use to extract iron from its ore?

Blast furnace.

State which substance the iron ore (hematite) contains and its function in the blast furnace.

It contains iron oxide(Fe2O3).
It is the compound that iron is extracted from.

State which substance coke contains and its function in the blast furnace.

It contains carbon(C) used as a fuel and reacts with oxygen to form carbon monoxide. This is needed to reduce the iron oxide.

State which substance limestone contains and its function in the blast furnace.

It contains calcium carbonate(CaCO3).
This helps to remove acidic impurities from the iron by reacting with it. This will form molten iron.

What are the reactions involved in the extraction of iron in a blast furnace?

1. The process is a reduction process.
2. Coke reacts with oxygen in the air to form carbon dioxide (exothermic combustion reaction).
3. The carbon dioxide reacts with more coke to form carbon monoxide (the carbon dioxide is reduced).
4. The iron oxide reacts with the coke or carbon monoxide and is reduced to form molten iron.

Explain how the blast furnace works.

1. Raw materials(iron ore, limestone, air & coke) are added to the top.
2. Blasts of hot air are blown near the bottom
3. Oxygen in this air reacts with the coke(carbon) to form carbon monoxide(CO).
4. This reaction is exothermic as the furnace reaches 2000 degrees Celsius.
5. Carbon monoxide rises and reacts with iron ore(iron oxide) to form iron. This is because carbon is more reactive than iron so will displace it from iron oxide.
6. Molten iron runs to the bottom and is tapped off.
7. This is used to make steel or will be solidified.

How are impurities removed from the iron ore in a blast furnace?

1. The main impurity in the mixture is silicon dioxide (sand).
2. Limestone undergoes thermal decomposition into calcium oxide.
3. The calcium oxide reacts with the silicon dioxide to form solid calcium silicate (slag) which can be removed from the furnace.
4. This is a neutralisation reaction.

What are uses of slag?

It used for roads and buildings.

How does electrolysis work?

● When a metallic compound is melted or dissolved, the ions are free to move within the liquid or solution.
● Passing a current through molten liquids or solutions means that the solution can be broken down into elements.
● During electrolysis the substance being broken down is the electrolyte.

What happens during the electrolysis of molten ionic compounds (e.g. lead bromide)?

● Pb2+ ions are positively charged so these ions move to the cathode and lead is produced at the cathode.
● The half equation at the cathode is:
Pb2+ (aq) + 2e\- -\>Pb (s)
● Br- ions are negatively charged so these ions move to the anode where two bromide ions lose an electron each to form liquid bromine.
● The half equation at the anode is:
2Br- (aq) -\> Br2 (l) + 2e-

Explain the process of the industrial extraction of aluminium.

● Aluminium oxide is melted so electricity can be passed through it.
● Aluminium oxide is dissolved in cryolite which is a substance that lowers melting point.
● Aluminium metal forms at the negative electrode and sinks to the bottom of the tank.
● Oxygen forms at the positive electrode and reacts with the carbon in the graphite electrodes forming CO2.
● The positive electrode has to be replaced often to account for the reaction of carbon and oxygen.

What are the properties and uses of iron?

● Malleable.
● An alloy, steel, can be formed from iron and carbon.
● Steel is harder and stronger than iron and less likely to rust.
● Used to build cars and used in the construction industry.

What are the properties and uses of aluminium?

● Low density.
● Lightweight for its size.
● Resists corrosion due to the very thin layer of their oxides on the surface.
● Used in aircrafts, trains, overheard power cables, saucepans and cooking foil.

What are the properties and uses of copper?

● Good conductor of heat and electricity.
● Soft, easily bent and shaped (malleable).
● Resistant to corrosion (very unreactive).
● Used in electrical wiring, gas and water pipes, and plumbing in houses as copper doesn't react with water.

What are the properties and uses of titanium?

● Low density.
● Lightweight for its size.
● Resists corrosion.
● Used in fighter aircraft, artificial hip joints and pipes in nuclear power stations.

Where are the transition metals located on the periodic table?

Middle.

What are the general properties of transition metals?

● High melting points.
● Form coloured compounds.
● Have the ability to form ions with different charges.
● Most are malleable and ductile.
● Good conductors of both heat and electricity due to their delocalised electrons.
● Hard and strong.
● Less reactive than group 1 alkali metals.

What are the chemical properties of transition metals?

1. They form ions with different charges
2. Less chemically reactive than alkali metals
3. Their chemical compounds are coloured

What is the test for transition metals ions?

When sodium hydroxide (NaOH) is added:
○ Copper (II) ions give a blue precipitate
○ Iron (II) ions give a pale green precipitate
○ Iron (III) ions give a pale brown precipitate

What is an alloy?

- A substance made of a mixture of 2 or more elements, of which at least one is a metal.
- They are made by mixing molten metals.
- The composition of alloys can be changed to produce alloys with desired properties.

Explain what happens during the electrolysis of water.

- Electrolysis can be used to separate water into hydrogen gas and oxygen gas.
- Positively charged hydrogen ions move to the negative electrode and gain electrons in a reduction reaction.
- Negatively charged hydroxide ions move to the positive electrode and lose electrons to form water and oxygen in an oxidation reaction.

What are the half equations in the electrolysis of water?

At the cathode the equation is:
4H+ (aq) + 4e\- -\> 2H2 (g)

At the anode the equation is:
4OH- (aq) -\> 02 (g) + 2H20 (l) + 4e-

Explain what happens during the electrolysis of aqueous solution.

● An ionic solution contains the ions that make up the ionic compound, and the ions in water (OH- and H+).

● At the cathode, hydrogen is produced unless the positively charged ions in the ionic compound are from a metal less reactive than hydrogen - then this metal will be produced instead.

● At the anode, oxygen will be produced unless the ionic compound contains halide ions (Cl-, Br-, I-), in the case the halogen will be produced.

What are the electrode equations in the electrolysis of copper(II) chloride?

● At the cathode, since copper is less reactive than hydrogen, copper ions are reduced to solid copper:
Cu2+ (aq) + 2e\- -\> Cu (s)

● At the anode chloride ions are oxidised:
2Cl- (aq) -\> Cl2 (g) + 2e-

What are the electrode equations in the electrolysis of sodium chloride?

● At the cathode hydrogen ions are reduced as sodium is more reactive than hydrogen:
2H+ (aq) + 2e\- -\> H2 (g)

● At the anode chloride ions are oxidised:
2Cl- (aq) -\> Cl2 (g) + 2e-

What are the uses of electrolysis?

● Electroplating - Covering the surface of one metal with another metal e.g. jewellery coated in silver to make it silver-plated.
● Purification of copper
● Manufacture of sodium hydroxide, hydrogen gas and chlorine gas.

What factors must be considered when extracting metals?

● Site of extraction plants:
○ Good infrastructure, close to power station, near a city as a source for workers, away from built-up areas due to noise and pollution.

● The method used - reduction with carbon to be used where possible to lower energy and costs needed.

● Recycling - using recycling plants to recycle and reuse materials as opposed to extract new raw materials.