The Extraction of Metals

Question 1

What are the two ways in which metals can be extracted?

Answer 1

By electrolysis
By reduction with coke (carbon)

Question 2

Why are some metals extracted by electrolysis?

Answer 2

Some metals are extracted by electrolysis because they are more reactive and tightly combined with oxygen, so more energy is required to decompose them.

Question 3

Why are some metals extracted by reduction with coke?

Answer 3

Some metals are extracted by reduction with coke because they are less reactive and less tightly combined with oxygen, so less energy is required to decompose them.

Question 4

Explain the process of the extraction of metals by reduction with coke

Answer 4

Step 1: Metal ores like sulphides and carbonates are first
roasted in air to change them into oxides.

Step 2: The metal oxides are then heated strongly with coke
(carbon) in a furnace.

Step 3: Reduction takes place and the metal is formed.

E.g. ZnO(s) + C(s) 🡪 Zn(l) + CO(g)

Question 5

Explain the process of the extraction of metals by electrolysis

Answer 5

The metal ores are molten and electricity is passed into it. The
metal is deposited on the cathode.

E.g. The electrolysis of aluminium oxide produces aluminium.

Question 6

What is the equation at the cathode for extraction by electrolysis?

Answer 6

The reaction at the cathode is: Al3+(l) + 3e- 🡪 Al(l)

Question 7

What is the equation at the anode or extraction by electrolysis?

Answer 7

The reaction at the anode is: 2O2-(l) 🡪 O2(g) + 4e-

Question 8

What metals in the reactivity series can be extracted using electrolysis?

Answer 8

K
Na
Ca
Mg
Al

Question 9

What metals in the reactivity series can be extracted using coke?

Answer 9

Zn
Fe
Pb
Cu

Question 10

What is the name and formula for the main ore from which iron is extracted?

Answer 10

Haematite or iron(III) oxide
Formula: Fe2O3

Question 11

How is iron extracted from its ore?

Answer 11

Iron is extracted from its ore by reduction with coke in a blast furnace

Question 12

What is the first step to extracting iron in a blast furnace?

Answer 12

A mixture of iron ore, coke and limestone are added from the top of the furnace.

Question 13

What is the second step in extracting iron in a blast furnace?

Answer 13

Hot air is blown in from the sides of the furnace.

Question 14

What is the third step in extracting iron in a blast furnace?

Answer 14

The coke burns in the hot air to form carbon dioxide and heat:
C(s) + O2(g) 🡪 CO2(g) + heat

Question 15

What is the fourth step to extracting iron in a blast furnace?

Answer 15

The carbon dioxide reacts with more coke to form carbon monoxide:
CO2(g) + C(s) 🡪 2CO(g)

Question 16

What is the fifth step to extracting iron in a blast furnace?

Answer 16

The carbon monoxide then reduces the iron(III) oxide to iron:
Fe2O3(s) + 3CO(g) 🡪 2Fe(l) + 3CO2(g)

Question 17

What is the sixth step to extracting iron in a blast furnace?

Answer 17

The molten iron sinks to the bottom of the furnace.

Question 18

What is the seventh step to extracting iron in a blast furnace?

Answer 18

The limestone breaks down to
form calcium oxide which
reacts with the impurities in iron
ore (SiO2) to form slag,
CaO(s) + SiO2(s) 🡪 CaSiO3(l)

Question 19

What is the eighth step to extracting iron in a blast furnace?

Answer 19

The slag floats on top of
the molten iron and can be
removed separately.