ion testing Flashcards

1
Q

Describe how to carry out a flame test to test for ions

A

Clean a nichrome wire using hydrochloric acid
Turn the bunsen burner onto the blue flame
Dip the wire into the substance being tested
Place the wire in the flame and record the colour

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2
Q

Colour of the flame test on lithium

A

Crimson

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3
Q

Colour of the flame on sodium

A

Yellow

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4
Q

Colour of the flame on potassium

A

Lilac

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5
Q

Colour of the flame on Calcium

A

Orange-red

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6
Q

Colour of the flame on copper

A

Blue-green

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7
Q

Why must the nichrome wire be cleaned first before carrying out a flame test?

A

To remove any unwanted ions that might obscure the colour of the flame

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8
Q

What is a precipitate

A

An insoluble solid suspended in a liquid

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9
Q

What colour precipitate forms when sodium hydroxide reacts with calcium

A

White

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10
Q

What colour precipitate forms when sodium hydroxide reacts with copper (II)

A

Blue

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11
Q

What colour precipitate forms when sodium hydroxide reacts with iron (II)

A

Green

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12
Q

What colour precipitate forms when sodium hydroxide reacts with iron(III)

A

Brown

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13
Q

What colour precipitate forms when sodium hydroxide reacts with aluminium

A

White, but with excess NaOH, the precipitate re-dissolves to form a colourless solution

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14
Q

What is observed when sodium hydroxide reacts with ammonium ions?

A

A pungent-smelling gas is produced (NH3) which will turn damp red litmus paper blue

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15
Q

How could you distinguish between two solutions containing aluminium ions and calcium ions?

A

Add excess sodium hydroxide. Both will form white precipitates initially. The precipitate formed from aluminium ions will re-dissolve to form a colourless solution.

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16
Q

How can you test for carbonate ions?

A

Add a few drops of HCL to the sample in a test tube.
Connect this test tube to a test tube of limewater. If carbonate ions are present, they will react with the acid to produce carbon dioxide, which will turn the limewater cloudy when it is bubbled through limewater

17
Q

How can you test for sulfate ions?

A

Add HCl to remove any co3 (2-) ions as these will obscure the results.
Add a couple of drops of barium chloride.
If sulfate ions are present a white precipitate of barium sulfate will form

18
Q

How do you carry out a test for halide ions?

A

Add a few drops of nitric acid to react with any carbonate ions which might obscure the result.
Add a couple of drops of silver nitrate
Observe the colour of the precipitate

19
Q

What colour precipitate forms when silver nitrate is added to a chloride solution?

A

A white precipitate

20
Q

What colour precipitate forms when silver nitrate is added to a bromide solution?

A

Cream

21
Q

What colour precipitate forms when silver nitrate is added to an iodide solution?

A

Yellow precipitate