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Word equations – information sheet
Word equations are shorthand used by scientists to describe chemical reactions.
Although there are many millions of possible chemical reactions, you are not expected to know
about all of them.
It is useful to remember that many reactions are of similar types.
1. Metal + acid
One type of reaction is that between a metal and an acid. When a metal reacts with an acid, the
reaction produces a salt, and hydrogen gas is released. The salt produced depends upon the metal
and the acid. If zinc reacts with hydrochloric acid, then the salt produced is zinc chloride.
metal + acid  salt + hydrogen
2. Metal carbonate + acid
Metal carbonates also react with acid to give a salt. When a carbonate reacts with acid, the gas
carbon dioxide is given off. The salt produced depends upon which acid and which metal
carbonate react. If calcium carbonate reacts with hydrochloric acid, then the salt produced is
calcium chloride. Water is also formed.
metal carbonate + acid  salt + carbon dioxide + water
3. Acid + alkali (i.e. a base that dissolves in water)
When an alkali and an acid react, the product is a salt and water. The particular salt produced
depends upon which acid and which alkali reacted. When hydrochloric acid reacts with sodium
hydroxide, the salt produced is sodium chloride.
acid + alkali  salt + water
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4. Group 1(Alkali) metals + air
The alkali metals in group 1 of the periodic table react with oxygen in the air to form oxides
When two elements react together to form a compound, the compound is given a name to show
which elements reacted. For example, when sodium reacts with oxygen the compound is called
sodium oxide.
Alkali metal + oxygen (in air)  metal oxide
5. Group 1(Alkali) metals + water
The alkali metals in group 1 of the periodic table are so called because, when they react with
water, they form alkalis (soluble bases) and hydrogen. When lithium reacts with water, it forms
lithium hydroxide and hydrogen.
Alkali metal + water  metal hydroxide + hydrogen
6. Metal + non-metal (element + element)
When two elements react together to form a compound, the compound is given a name to show
which elements reacted. For example, when calcium reacts with chlorine, the compound is called
calcium chloride.
These examples show the patterns that are found in six important types of reaction. If you look
for patterns, you should find it easier to work out how to complete word equations.
In the worksheets you will find some examples to help you practise thinking about word
equations.
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