Please enable JavaScript.
Coggle requires JavaScript to display documents.
C5: Chemical changes (5.7: Neutralisation and the pH scale (The pH scale…
C5: Chemical changes
-
-
5.3: Extracting metals
Mining ores often involves digging up large amounts of rock - the metal ore may need to be concentrated before the metal is extracted - these processes can produce large amounts of waste and may have major impacts on the environment
-
A few unreactive metals, such as gold, that are low in the reactivity series, are found in the earth as the metal - gold can be separated from rocks by physical methods
However, most metals are found as compounds - these metals have to be extracted by chemical reactions
-
Metals that are less reactive than carbon can be extracted from their oxides by heating with carbon - a reduction reaction takes place as carbon removes the oxygen from the oxide to produce the metal - this method is used commercially if possible (e.g. lead oxide + carbon -> lead + carbon dioxide)
The metals that are more reactive than carbon are not extracted from their ores by reduction with carbon - instead they're extracted by electrolysis of the molten metal compound
-
5.4: Salts from metals
-
However, the reactions of acids with very reactive metals (e.g. sodium or potassium) are too violent to carry out safely
When metals react with acids, they produce a salt and hydrogen gas (acid + metal -> a salt + hydrogen
The salt produced depends on the metal and acid you use - magnesium metal always make salts containing magnesium ions
-
-
-
5.6: Making more salts
-
There is no visible change when acids react with alkalis so you need to use an indicator or a pH meter to show when the reaction is complete - the solid salt can be obtained from the solution by crystalisation
You can also make soluble salts by reacting an acid and a carbonate (e.g. acid + a carbonate -> a salt + water + carbon dioxide)
For calcium carbonate, the reaction with hydrochloric acid is: calcium carbonate + hydrochloric acid -> calcium chloride + water + carbon dioxide