What does soluble and What does soluble and insoluble mean?insoluble mean?

What would be produced when something is insoluble?

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Making a salt!Making a salt!

They love an exam question on this!

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Making a salt

Lead nitrate and potassium iodide are soluble in water. They react to make Lead iodide and Potassium nitrate. Lead iodide is a yellow precipitate and so is insoluble. It could be removed by filtering the mixture, washing it with water to clean it and then drying it using a Bunsen burner or warm oven.

How can we test for How can we test for ions?ions?

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Ion tests

Flame tests are used to identify the metal ion in a salt.

Dip the flame test loop in acid to clean it. Hold it in the flame to check it is clean, if it is not, put it in acid again. When clean, dip the loop into the sample and hold the loop in the flame.

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Flame testsFlame testsCompounds containing lithium, sodium, potassium, calcium and barium ions can be recognised by burning the compound and observing the colours produced:

Lithium

Red

Sodium

Yellow

Potassium

Lilac

Calcium

Brick red

Barium

Green

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Testing for carbonate ionsTesting for carbonate ions

Limewater turns milky/cloudy

Limewater

Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water

What does this tell us is being made?

Test for carbonate ions CO3-

Carbon dioxide gas is given off when an acid is added to a substance containing carbonate ions.Limewater is used to identify the gas given off. If the limewater changes colour from colourless to cloudy / milky white then the gas is Carbon dioxide.

21/04/23Testing for chloride and sulfate Testing for chloride and sulfate ionsions

Test 1: Chloride ions

Add a few drops of dilute nitric acid to the chloride ion solution followed by a few drops of silver nitrate.

Test 2: Sulphate ions

Add a few drops of dilute hydrochloric acid to the sulphate ion solution followed by a few drops of barium chloride.

Precipitate formed = silver chloride (white)

Precipitate formed = barium sulphate (white again)

For each test state: 1) The colour of the precipitate

2) What compound it is

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SpectroscopySpectroscopySpectroscopy is kind of like a flame test but using a “spectroscope” to see the results:

Using this spectroscope I can see this:

Each different element has a different “signature” when viewed through a spectroscope. This analysis enables us to detect the presence of small amounts of elements and this led to the discovery of new elements including rubidium and caesium.