Acids and Bases
The pH scale is a measure of how acidic or alkaline a solution is
The lower the pH of a solution, the more acidic it is
The high the pH of a solution, the more alkaline it is
A neutral substance has pH 7
An indicator is a dye that changed colour depending on whether it’s above or below a certain pH
Some indicators contain a mixture of dyes meaning they gradually change colour
Called wide range indicators for example universal indicator
A pH probe attached to a pH meter can also be used to measure pH electronically
The probe is placed in the solution you are measuring and the pH is given on a digital display as a numerical value meaning its more accurate
An acid is a substance that forms aqueous solution with a pH of less than 7
Acids form H+ions in water
A base is a substance with a pH greater than 7
An alkali is a base that dissolves in water to form a solution with a pH greater than 7
Alkalis form OH-ions in water
The reaction between acids and bases is called neutralisation:
Acids + base - salt + water
Neutralisation between acids and alkalis can be seen in terms on H+ and OH-ions:
H+ + OH- - H20
When an acid neutralises a base the products are neutral
An indicator can be used too show that a neutralisation reaction is over
Neutralisation reactions of strong acids and alkalis can be used to calculate the concentration of an acid or alkali by titration, there is more about this technique
The pH scale is a measure of how acidic or alkaline a solution is
The lower the pH of a solution, the more acidic it is
The high the pH of a solution, the more alkaline it is
A neutral substance has pH 7
An indicator is a dye that changed colour depending on whether it’s above or below a certain pH
Some indicators contain a mixture of dyes meaning they gradually change colour
Called wide range indicators for example universal indicator
A pH probe attached to a pH meter can also be used to measure pH electronically
The probe is placed in the solution you are measuring and the pH is given on a digital display as a numerical value meaning its more accurate
An acid is a substance that forms aqueous solution with a pH of less than 7
Acids form H+ions in water
A base is a substance with a pH greater than 7
An alkali is a base that dissolves in water to form a solution with a pH greater than 7
Alkalis form OH-ions in water
The reaction between acids and bases is called neutralisation:
Acids + base - salt + water
Neutralisation between acids and alkalis can be seen in terms on H+ and OH-ions:
H+ + OH- - H20
When an acid neutralises a base the products are neutral
An indicator can be used too show that a neutralisation reaction is over
Neutralisation reactions of strong acids and alkalis can be used to calculate the concentration of an acid or alkali by titration, there is more about this technique