Water testing

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chemical analysis

Food and other products are tested for purity and safety by chemicals. There are two main types:

Qualitative analysis: investigates the kind of substances present in a sample.

Quantitative analysis: measures the amount of each substance present.

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Flame Tests

Water often contains ionic compounds, to identify these ions tests must be carried out. 

One of these tests are flame tests, each ion gives off different colours to detect them.

Calcium creates a brick red colour.

Sodium a yellow colour

Potassium creates lilac colour.

Copper creates a greeny bluey colour.

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Precipitate test.

To test for other cations, sodium hydroxide is added to the solution and a precipitate reaction occurs. 

Aluminium creates a white precipitate

Calcium creates a white precipitate

Copper creates a pale blue precipitate

Iron 2 creates a green precipitate

Iron 3 creates a brown, rust precipitate 

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determine between aluminium and calcium

Aluminium and calcium can be determined by adding excess sodium hydroxide.

The calcium will remain unchanged. 

The aluminium ion dissolves into a cloudless solution

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