Higher and foundation tier

Neutralisation using metal carbonates

antacids

Good bases include metal oxides, solid metal hydroxides (remember solutions of metal hydroxides are called alkalis) and metal carbonates. All these bases can be used to neutralise acids. Metal carbonates including calcium carbonate and magnesium carbonate are often used to neutralise acids. Calcium carbonate is the main ingredient in antacid tablets. Indigestion is caused by too much acid being produced in the stomach. To neutralise this excess acid a non-toxic base is need and calcium carbonate (or chalk) is ideal. Acids react with metal carbonates according to the equation below:

acid(aq) + metal carbonate(s) salt (aq) + water(l) + carbon dioxide(g)

copper carbonate reacting with hydrochloric acid

When metal carbonates reacts with acids they fizz due to the carbon dioxide gas which is released. The image opposite shows copper carbonate reacting with hydrochloric acid. The carbon dioxide gas which is released can be detected by simply bubbling it through a solution of limewater. The limewater will turn a milky or chalky colour in the presence of carbon dioxide gas. When the reaction has finished, that is no more bubbles of carbon dioxide gas are seen, then the acid has been neutralised.

To obtain the solid copper chloride salt the solution will need to be filtered and evaporated, this is outlined in the diagram below. This simple experiment produced the salt copper chloride, obviously different salts can be produced by simply using different acids.

Neutralisation and metal carbonates- basic method

The method used to neutralise an acid using a metal carbonate is shown below. It is very similar to the method described earlier using copper oxide as a base. In this example the metal carbonate used is calcium carbonate (chalk) and the acid used is hydrochloric acid.

neutralisation of an acid using a metal carbonate

Practice questions

Check your understanding - Questions on metal carbonates and acids

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