Chemistry - Acids and Alkalis

Chemistry 2 (iii) - Using Ions in Solution

Acids and Alkalis

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Chemistry - Acids and Alkalis

An Indicator is Just a Dye That Changes Colour

the dye in the indicator changes colour depending on whether it's above or below a certain pH. Universal Indicator is a very useful combination of dyes which gives the colours shown above (red/green/blue). It's very useful for estimating the pH of a solution.

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Chemistry - Acids and Alkalis

The pH Scale Goes From 0 to 14

1) The strongest acid has pH 0. The strongest alkali has pH 14

2) A neutral substance has pH 7 (e.g. pure water).

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Chemistry - Acids and Alkalis

Acids and Bases Neutralises Each Other

An ACID is a substance with a pH of less than 7. Acids form H+(aq) ions in water.

A BASE is a substance with a pH of greater than 7.

An ALKALI is a base that dissolves in water. Alkalis form OH-(aq) ions in water

The reaction between acids and bases is calkled neutralisation. Make sure you learn it:

acid + base --> salt + water

Neutralisation can also be seen in terms of H+ and OH- ions like this, so learn it too:

H+(aq) + OH-(aq) --> H20 (l)

When an acid neutralises a base (or vice versa), the products are neutral, i.e they have a pH of 7.

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