TWEED RIVER HIGH SCHOOL
2006
PRELIMINARY CHEMISTRY
Unit 2
Metals
Part 5

Define the terms mineral and ore with reference to economic and non-economic
deposits of natural resources.
Minerals usually occur in nature as mixtures with other minerals. If the mineral is
present in sufficient quantity to make the mining and extraction of the metal
economically viable it is called an ore. An ore is defined as a naturally occurring
deposit that is a mixture of minerals from which a substance, usually a metal, can be
economically extracted.

Describe the relationship between the commercial prices of common metals,
their abundances and relative costs of production.
An ore must contain a sufficient quantity of a particular mineral to make mining of
the ore and eventual extraction of the metal an economic proposition. For example,
copper makes up only about 0.007% of the earth’s lithosphere but it can exist in ores
containing minerals such as malachite and chalcopyrite in sufficient concentration to
make the mining and extraction of the copper an economic option.
Factors that affect the commercial price and extent to which particular metals are used
in the community include:
1. the actual abundance of the metal in exploitable ores
2. the cost of extraction of the metal
3. the demand for the metal
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Titanium is a highly sought after metal despite its relative rarity in exploitable ores.
The particular properties that make titanium a highly sought metal include its extreme
toughness and durability and resistance to corrosion. As a result titanium is quite an
expensive metal.

Explain why ores are non-renewable resources.
Non-renewable resources cannot be replaced once they are used. That is once ores
have been mined, they cannot be replaced.

Describe
the
separation
processes,
chemical
reactions
and
energy
considerations involved in the extraction of copper from its ores.

Copper is extracted principally from sulfide ores, particularly chalcopyrite
(CuFeS2).

A smelting process is used to obtain crude copper of about 98% purity.
In this process, strong heating of the ore oxidises the sulfide to gaseous sulfur
dioxide and reduces the copper to metal.
The reaction occurs in a series of steps and is summarised as:
2CuFeS2(s) + 5O2(g) + SiO2(s)  2Cu(l) + 4SO2(g) + 2FeSiO3(l)

The crude ore often contains less than 0.5% copper.

The crude ore is concentrated by froth flotation.

The concentrated ore, now about 15%, is then roasted in air which oxidises the
FeS to FeO but leaves CuS unaffected.
2CuFeS2(s) + 3O2(g) +  2CuS(s) + 2FeO(s) + 2SO2(g)

This product is then heated at 1100C with ground limestone, sand and
additional concentrated ore.

This converts the FeO to molten slag and reduces the copper(ll) sulfide to
copper(l) sulfide.
FeO(s) + SiO2(s)  FeSiO3(l)
2

In the final smelting step the copper(l) sulfide is roasted in air so that
part of it is converted to copper(l) oxide.
2Cu2S(s) +3O2(g)  2Cu2O(s) + 2SO2(g)

The two copper(l) compounds, copper(l) sulfide and copper(l) oxide,
then react together to form copper metal and sulfur dioxide.
2Cu2O(s) + Cu2S(s)  6Cu(l) + SO2(g)

This process requires a significant input of energy to maintain the
temperatures required for this reaction.

The copper produced is called blister copper due to escaping sulfur
dioxide.

To obtain 99.9% copper purity required for electrical wiring, the blister
copper is refined electrolytically..
Copy Fig 10.6 p162 Text
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
Justify the increased recycling of metals in our society and across the world.

As mineral resources are not renewable, their extraction or recycling have to
be extended.

Mineral resources are being extended by:
1. New ore bodies are being discovered
2. Improving technology has increased the ability to access ores
3. The ability to extract metals from lower grade ores is improving
4. Improved corrosion protection of metals has extended their use.

Despite all these improvements, ores are non-renewable and hence the
increase in recycling. Recycling also requires a much lower energy input. Both
extending the limited resources of the metal and reduces cost of production.

Many metals such as iron, copper, steel and aluminium are recycled.

Recount the steps taken to recycle aluminium.

Analyse information to compare the cost and energy expenditure involved in the
extraction of aluminium from its ore and the recycling of aluminium.
Summarise pages 165 and 166, Chemistry Contexts 1. Include Figure 10.7 and
chemical equations.
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