4.6 Separating Metals from Metal Oxides

How to separate pure metals from metal oxides The definitions of oxidation and reduction How carbon can be used to obtain some metals from ores

oxidation

the process of gaining oxygen

reduction

the loss of oxygen

how to remove oxygen to obtain a pure metal

reacting metal oxide with carbon

electrolysis

extracted by reduction with carbon

carbon will take the oxygen from the metal to form carbon dioxide and leave behind a pure metal

carbon oxide + carbon

carbon oxide (reduced) + carbon (oxidised) → copper + carbon dioxide

what metals can carbon extract

zinc, iron, copper

ores

metal rich compounds

native

unreactive metals, found as elements in nature

Why do we find pure gold in the ground, but not pure iron?

Gold is unreactive, so doesn't react with any other elements

Iron is reactive enough to react with oxygen so is oxidised to iron oxide 

Electrolysis

Electrolysis is needed to extract these metals because their oxides cannot be reduced by carbon

ways of extraction from elements in the reactivity series

a more reactive element will push out (displace a less reactive element in its compound

Where are most metals found?

Earth’s Crust

What is panning?

physical separation of native metals

Give three factors that make it economically viable to extract metal?

How easy it is to extract from its ore

How much metal the ore contains

The changing demands for a particular metal.

How are most metals extracted the earth?

Mining

Why is hydrogen not generally used to extract metals?

More expensive than carbon

Why is carbon used to extract metals?

Cheap and readily available

How do we extract metals above carbon in the reactivity series and why can’t we use carbon to extract them?

Electrolysis

Carbon is below them in the reactivity series (less reactive) so cannot displace them

Explain how reduction by carbon works?

During the reaction, the metal in the ore is displaced fromits non-metal anion because carbon is more reactive thanthe metal.

Why don’t we generally use “reduction” to extract metals above carbon in the reactivity series and what is the only exception?

more expensive than electrolysis and is only

used on a commercial scale for the extraction of titanium.

Give two alternative names for carbon

coke and Charcoal

metal oxide + carbon

metal oxide + carbon → metal + carbon dioxide

iron(III) oxide + carbon → iron + carbon dioxide

2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)

how is iron extracted

a large reaction vessel called a blat furnace

explain which chemicals are being oxidised and which are being reduced and which is not possible