C3 - Water Testing (testing for metal cations)

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  • Created by: kat-y
  • Created on: 01-11-16 17:20
Define QUALITATIVE analysis
Investigating what kind of chemicals are in a sample
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Define QUANTITATIVE analysis
Measuring HOW MUCH of certain chemicals there are in a sample
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What are flame tests used to detect?
Some metal cations
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Calcium is..........in a flame test
Brick red
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Sodium is..........in a flame test
Yellow
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Potassium is...........in a flame test
Lilac
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Copper is........in a flame test
Green/Blue
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What is the other test for other cations?
Adding drops of sodium hydroxide to the solution with the unknown substance
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How does the sodium hydroxide test work?
A precipitation reaction occurs when the NaOH is added to a solution the unknown substance, due to the fact that many metal hydroxides are insoluble. You can identify the ion by observing the precipitate formed.
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A precipitate is an...........solid formed when two.........are mixed together and a precipitation reaction occurs
insoluble, solutions
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What is a precipitate reaction?
A reaction by two soluble reactions and a insoluble product is formed.
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What is the effect of adding NaOH to aluminium?
A white precipitate is formed
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When NaOH is added to calcium......
A white precipitate is formed
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When NaOH is added to copper(II)........
A pale blue precipitate is formed
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When NaOH is added to iron(II)......
A green precipitate is formed
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When NaOH is added to iron(III).....
A brown(rust) precipitate is formed
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What method distinguishes aluminium ions from calcium ions?
By adding more NaOH
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How does this method work?
The aluminium ion precipitate REDISSOLVES to form a colourless solution in EXCESS NaOH. The calcium ion precipitate remains unchanged.
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Why is it important for the test of any ion to be unique?
Because if the test gave a positive result for two or more ions then you would not be sure which was present in the compound.
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Other cards in this set

Card 2

Front

Define QUANTITATIVE analysis

Back

Measuring HOW MUCH of certain chemicals there are in a sample

Card 3

Front

What are flame tests used to detect?

Back

Preview of the front of card 3

Card 4

Front

Calcium is..........in a flame test

Back

Preview of the front of card 4

Card 5

Front

Sodium is..........in a flame test

Back

Preview of the front of card 5
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