SS 2 – SS3
Read up the following topics:
(b) Metals and their compounds
1. New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio
2. IGCSE Chemistry by Earl Wilford
Answer the following Questions
1. Lactic acid can be made from corn starch.
It polymerises to form the polymer, polylactic acid (PLA ) which is biodegradable.
(a) Suggest two advantages that PLA has compared with a polymer made from petroleum.
(b) The structure of PLA is given below.
(i) What type of compound contains the group that is circled?
(ii) Complete the following sentence.
Lactic acid molecules can form this group because they contain both an--------------------- group and an------------------------------------- group. 
(iii) Name a synthetic polyester. 
(iv) Is the formation of PLA, an addition or condensation polymerisation? Give a reason for your choice. 
2. (a) Alkenes can polymerise.
(i) Deduce the name and structural formula of the monomer from the structure of the
(ii) Draw the structure of the polymer formed from the following monomer.
(iii) Compare the structure of a protein with that of a synthetic polyamide. The structure of a typical protein is given below.
How are they similar?
How are they different? 
3. No one knows where iron was first isolated. It appeared in China, the Middle East and in Africa. It was obtained by reducing iron ore with charcoal.
(a) Complete the following equation.
Fe2O3 + C → ................... + ........................
iron ore charcoal 
(b) In 1705 Abraham Darby showed that iron ore could be reduced using coke in a blast furnace.
(i) The temperature in the furnace rises to 2000 °C. Write an equation for the exothermic reaction that causes this high temperature.
(ii) In the furnace, the ore is reduced by carbon monoxide. Explain how this is formed. 
(c) Stainless steel is an alloy of iron. It contains iron, other metals and about 0.5% of carbon.
(i) State a use of stainless steel.
(ii) Name a metal, other than iron, in stainless steel.
(iii) The iron from the blast furnace is impure. It contains about 5% of carbon and other impurities, such as silicon and phosphorus. Describe how the percentage of carbon is reduced and the other impurities are removed. 
(d) One of the methods used to prevent iron or steel from rusting is to electroplate it with
another metal, such as tin. Complete the following.
The anode is made of ............................................... .
The cathode is made of ............................................. .
The electrolyte is a solution of ................................... . 
4. (a) Aluminium is extracted by the electrolysis of its molten oxide.
(i) Name the main ore of aluminium.
(ii) Why does the molten electrolyte contain cryolite?
(b) The ions that are involved in the electrolysis are Al3+ and O2-.
(i) Write an equation for the reaction at the cathode.
(ii) Explain how carbon dioxide is formed at the anode.
(c) Give an explanation for each of the following.
(i) Aluminium is used extensively in the manufacture of aircraft.
(ii) Aluminium is used to make food containers.
(iii) Aluminium electricity cables have a steel core.