Topic 6: Global Challenges - Subtopic 1: Improving Processes & Products
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What is a metal ore?
• Rock that contains enough of the metal to make it worthwhile extracting
Give two examples of oxide ores and their corresponding metals.
Haematite (iron ore) and bauxite (aluminium ore).
What are native metals?
Unreactive metals that are found as the uncombined element and can be mined directly from the Earth’s crust.
Give two examples of native metals.
Gold and platinum.
What determines the method of extraction for a metal?
The position of the metal on the reactivity series.
How are metals placed above carbon in the reactivity series extracted?
Using electrolysis.
How are metals placed below carbon in the reactivity series extracted?
By heating with carbon which reduces them.
What are the two stages in extracting copper from copper sulfide?
Stage 1: Heating copper sulfide in air to produce copper oxide. Stage 2: Reducing copper oxide with carbon to produce copper.
Write the equation for heating copper sulfide in air.
2CuS (s) + 3O2 (g) → 2CuO (s) + 2SO2 (g)
Write the equation for reducing copper oxide with carbon.
2CuO (s) + C (s) → 2Cu (s) + CO2 (g)
What type of reaction occurs when extracting copper?
A redox reaction where both reduction and oxidation take place.
What is the name of the large container used to extract iron?
A blast furnace.
How much iron do modern blast furnaces produce per day?
Approximately 10000 tonnes of iron per day.
What are the three raw materials added to a blast furnace when extracting iron?
Iron ore (haematite) coke (an impure form of carbon) and limestone.
What happens in Zone 1 of the blast furnace when extracting iron?
Coke burns in hot air forming carbon dioxide: C (s) + O2 (g) → CO2 (g)
What happens in Zone 2 of the blast furnace when extracting iron?
Coke reacts with carbon dioxide forming carbon monoxide: CO2 (g) + C (s) → 2CO (g)
What happens in Zone 3 of the blast furnace when extracting iron?
Carbon monoxide reduces iron (III) oxide to form iron: Fe2O3 (s) + 3CO (g) → 2Fe (l) + 3CO2 (g)
Why is limestone added to the blast furnace when extracting iron?
To remove impurities in the ore.
What does calcium carbonate in limestone decompose to form?
Calcium oxide: CaCO3 (s) → CaO (s) + CO2 (g)
What impurity does calcium oxide react with in the blast furnace when extracting iron?
Silicon dioxide (an impurity in iron ore).
What is formed when calcium oxide reacts with silicon dioxide?
Calcium silicate: CaO (s) + SiO2 (s) → CaSiO3 (l)
What is slag in the context of iron extraction?
Molten calcium silicate that floats on top of molten iron and is tapped off separately.
Why are some metals extracted using electrolysis?
Because they are too reactive to be reduced by carbon.
Give an example of a metal extracted by electrolysis.
Aluminium from aluminium oxide (bauxite).