Qualitative Analysis

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Why do we test ionic compounds?
It allows us to identify the positive and negative ions within the compounds.
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Discuss the mystery compound.
It is possible to see if the compound to contain more than 2 ions as each type of ion has an individual result, so if theres more than 2 it still works.
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How do you test for positive ions in ionic compounds?
You add a few drops of sodium hydroxide to a solution of the mystery compound.
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What should the solution form with the sodium hydroxide?
It should form an insoluble hydroxide that has a unique colour.
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Why does this test work?
Because many metal hydroxides are insoluble and precipitate out of solution when formed which is what happens here.
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What happens when NaOH is added to calcium?
A white precipitate forms
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What happens when NaOH is added to copper II?
A blue precipitate forms.
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What happens when NaOH is added to iron II?
A green precipitate forms
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What happens when NaOH is added to iron III?
A brown precipitate forms.
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Why does this test have to be adjusted for aluminium?
Aluminium doesn't form uniquely at first, as it forms a white precipitate like calcium does. Therefore, we have to add more NaOH until it dissolves to form a colourless solution.
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How do you test for ammonium ions?
You warm the substance gently with NaOH. If ammonia is present, a stinky alkaline gas is given off which turns damp red litmus paper blue.
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How do you test for halides?
Add dilute nitric acid and silver nitrate to a solution.
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What happens if a chloride is present?
A white precipitate of silver chloride will form.
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What happens if a bromide is present?
A cream precipitate of silver bromide will form.
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What happens if an iodide is present?
A yellow precipitate of silver iodide will form.
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What colours are potassium, copper, calcium and sodium in flame tests?
Potassium is purple, copper is blue/green, calcium is red and sodium is yellow/orange.
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How do you test for a sulfate?
Hydrochloric acid + barium chloride ---> barium sulfate (white precipitate)
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How do you test for carbonates?
Add dilute acid to the solution and if a carbonate is present carbon dioxide will be given off which turns limewater milky.
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Other cards in this set

Card 2

Front

Discuss the mystery compound.

Back

It is possible to see if the compound to contain more than 2 ions as each type of ion has an individual result, so if theres more than 2 it still works.

Card 3

Front

How do you test for positive ions in ionic compounds?

Back

Preview of the front of card 3

Card 4

Front

What should the solution form with the sodium hydroxide?

Back

Preview of the front of card 4

Card 5

Front

Why does this test work?

Back

Preview of the front of card 5
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