Chemistry 2.3 Metals and Their Extraction

Metal extraction

Metals are extracted from ores which are rocks containing metal compounds using chemical reactions

Metal reactivity and extraction

More reactive metals form more stable compounds so are harder to extract while unreactive metals may be found pure

Extraction methods

Eletrolysis for metals more reactive than carbon reduction with carbon for metals less reactive than carbon metals less reactive than hydrogen found native

Displacement reaction

A more reactive metal displaces a less reactive metal from a compound and is used to compare reactivity

Oxidation

Gain of oxygen loss of electrons or loss of hydrogen and the oxidised species is the reducing agent

Reduction

Loss of oxygen gain of electrons or gain of hydrogen and the reduced species is the oxidising agent

Iron extraction in a blast furnace

Coke burns to form carbon dioxide which forms carbon monoxide that reduces iron oxide to molten iron

Removal of impurities in blast furnace

Limestone decomposes to calcium oxide which reacts with silicon dioxide to form calcium silicate slag

Electrolysis

Using electricity to break down molten or dissolved ionic compounds into elements

Electrolysis of molten ionic compounds (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 Pb²⁺ (aq) + 2e^- → Pb (s)

Br^- ions are negatively charged so these ions move to the anode where two bromide ions lose an electron to form liquid bromine

The half equation at the anode is 2Br^- (aq) → Br₂ (l) +2e^-

Aluminium extraction

Aluminium oxide dissolved in cryolite is electrolysed aluminium forms at the cathode oxygen at the anode reacts with carbon electrodes

Properties and uses of iron

Malleable forms steel with carbon used in cars and construction

Properties and uses of aluminium

Low density corrosion resistant used in aircraft power cables and packaging

Properties and uses of copper

Good conductor malleable corrosion resistant used in wiring and plumbing

Properties and uses of titanium

Low density strong corrosion resistant used in aircraft medical implants and nuclear pipes

Properties of transition metals

High melting points coloured compounds variable ions good conductors hard and less reactive than group 1

Test for metal ions

Sodium hydroxide gives blue precipitate for copper two green for iron two brown for iron three

Alloy

A mixture of two or more elements at least one metal made by mixing molten metals to improve properties

Electrolysis of water

Water splits into hydrogen at the cathode and oxygen at the anode

Half equations for electrolysis of water

Cathode four H plus plus four electrons gives two H two anode four OH minus gives oxygen water and electrons

Electrolysis of aqueous solutions

Hydrogen forms at cathode unless metal is less reactive than hydrogen oxygen forms at anode unless halide ions present

Electrolysis of copper chloride

Copper forms at cathode chlorine forms at anode

Electrolysis of sodium chloride

Hydrogen forms at cathode chlorine forms at anode

Uses of electrolysis

Electroplating purification of copper and manufacture of sodium hydroxide hydrogen and chlorine

Factors in metal extraction

Location cost energy use method and recycling considerations