Chemistry C3 4.1 Tests for positive ions.

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How can Group 1 and Group 2 metal ions be identified?
Using a flame test.
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Depending on the precipitate that is formed, what can sodium hydroxide solution be used to identify?
Different metal ions.
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How can lithium ions and calcium ions be identified, and why is it difficult to do this using a flame test?
Both lithium ions and calcium ions give red flame test, lithium ions are a brighter red but it is difficult to tell them apart. Using solutions of the ions with sodium hydroxide solution: calcium ions give white precipitate but lithium ions do not.
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Why would a sodium hydroxide solution or a flame test be used?
To identify some positive ions.
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What colour does lithium (Li^+) produce in a flame test?
Crimson (red).
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What colour does sodium (Na^+) produce in a flame test?
Yellow.
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What colour does potassium (K^+) produce in a flame test?
Lilac.
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What colour does calcium (Ca^(2+)) produce in a flame test?
Red.
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What colour does Barium (Ba^(2+)) produce in a flame test.
Green.
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What do the hydroxides of most metals that have ions with 2+ and 3+ charges have in common?
They are insoluble in water, when sodium hydroxide is added to solutions of these ions a precipitate of the metal hydroxide forms.
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What does aluminium, calcium and magnesium ions all form?
White precipitates.
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What happens to the precipitate of aluminium hydroxide when odium hydroxide solution is added?
It dissolves.
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What colour is copper(II) hydroxide?
Blue.
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What colour is iron(II) hydroxide?
Green.
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What colour is iron(III) hydroxide?
Brown.
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Drops of sodium hydroxide solution were added to a colourless solution and a white precipitate appeared. Excess sodium hydroxide was added was added the precipitate remained, which metal ions could be present?
Calcium (Ca^2+) and magnesium (Mg^2+).
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Other cards in this set

Card 2

Front

Depending on the precipitate that is formed, what can sodium hydroxide solution be used to identify?

Back

Different metal ions.

Card 3

Front

How can lithium ions and calcium ions be identified, and why is it difficult to do this using a flame test?

Back

Preview of the front of card 3

Card 4

Front

Why would a sodium hydroxide solution or a flame test be used?

Back

Preview of the front of card 4

Card 5

Front

What colour does lithium (Li^+) produce in a flame test?

Back

Preview of the front of card 5
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