Page 14 - Curriculum Visions Dynamic Book

non-metals such as the halogens (e.g. chlorine), sulphur and oxygen in groups
6 and 7 toward the right of the Periodic Table.As a result, many of the compounds found on Earth contain these elements
as metal oxides, sulphides, sulphates and chlorides.
Carbon is a very common element, found both in organic compounds and also in an inorganic form called carbonate.
Obtaining elements from their compounds
There are many ways of obtaining elements from their compounds. Compounds can be broken down
with heat in a process called thermal decomposition or by applying electricity in a process called electrolysis. Compounds
 The electrolysis of brine to manufacture sodium hydroxide. Chlorine and hydrogen are also produced.
can also be broken down through chemical reduction (taking away oxygen). Each method is widely used because the majority of the world’s metals are found as compounds, usually chlorides, sulphides, oxides and carbonates.
All of the less reactive metals form mainly sulphide ores that will not dissolve (they are insoluble). On the other hand, many of the highly reactive metals form chloride compounds that are very soluble, for example, NaCl, sodium chloride, or common salt. Common salt is found dissolved in relatively low concentration in all the world’s freshwater lakes and rivers as well as in much greater concentration in the sea. Soluble compounds can be extracted directly by dissolving them, usually in hot water.
Hydrogen gas collected
Strong brine added
Chlorine gas collected
Electricity supply is passed through the cell, which is under pressure.
Concentrated sodium hydroxide is collected.
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