# 6.3.1 Strength of Acids and Alkalis

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## Strong Acids and Weak Acids

1. Acids are chemical substances that ionize/dissociate in the presence of water to produce hydrogen ions (or hydroxonium ions).
2. Acids can be classified into 2 categories:
1. Strong acids
2. Weak acids
3. The strength of an acid depends on the degree of ionization/dissociation of the acid.

### Strong Acids

Strong acids are acids that ionise completely to form hydrogen ions in water.
Examples:
Sulphuric acid
Hydrochloric acid
Nitric acid
##### Weak Acids
Weak acids are acids that partly ionise to form hydrogen ions in water.
Examples:
Ethanoic acid
Phosphoric acid
Citric acid

## Strength of Alkali​

1. Similar to the strength of acids, the strength of an alkali is defined by its ability to ionise and release hydroxide ions (OH) in the solution.
2. In a solution of strong alkali, all the alkali molecules are ionised in the water to produce hydroxide ions.
3. In a solution of weak alkali, only a small portion of the molecules are ionised to release hydroxide ions.
4. The table below shows some example of strong/weak alkalis.
 Alkali Strong Weak NaOHKOHLiOH NH3