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A Level Chemistry > 5.2.1 - Reactions and Colours of Metal Aqua Ions > Flashcards

5.2.1 - Reactions and Colours of Metal Aqua Ions Flashcards

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1
Q

Why are metal-aqua ion solutions acidic?

A

Hydrolysis occurs on the metal-aqua complex ions.

For example, [Fe(H₂O)₆]²⁺ (aq) + H₂O (l) —-> [Fe(OH)(H₂O)₅]⁺ (aq) + H₃O⁺ (aq)

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2
Q

Why are 3⁺ metal-aqua solutions more acidic than 2⁺ metal-aqua solutions?

A

3⁺ metal-aqua solutions have a higher charge density due to their higher charge and smaller size. This makes them more polarising. As they attract the bonding pair of electrons, the O-H gets weaker which means the H⁺ ion is more likely to be released.

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3
Q

What colour are [Cu(H₂O)₆]²⁺ ions?

A

Blue.

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4
Q

What colour are [Fe(H₂O)₆]²⁺ ions?

A

Green.

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5
Q

What colour are [Al(H₂O)₆]³⁺ ions?

A

Colourless.

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6
Q

What colour are [Fe(H₂O)₆]³⁺ ions?

A

Although the solution is actually purple, it appears yellow because one of the H₂O ligands hydrolyses.

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7
Q

What is the overall reaction for [Cu(H₂O)₆]²⁺ reacting with sodium hydroxide dropwise?

What colour does this turn?

A

[Cu(H₂O)₆]²⁺ + 2OH⁻ —-> Cu(H₂O)₄(OH)₂ + 2H₂O

It forms a blue precipitate.

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8
Q

Does [Cu(H₂O)₆]²⁺ react differently in an excess of NaOH?

A

No, it remains the same as dropwise.

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9
Q

What is the overall reaction for [Cu(H₂O)₆]²⁺ reacting with ammonia dropwise?

What colour does this turn?

A

[Cu(H₂O)₆]²⁺ + 2NH₃ —> Cu(H₂O)₄(OH)₂ + 2NH₄⁺

It forms a blue precipitate.

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10
Q

Does [Cu(H₂O)₆]²⁺ react differently in an excess of ammonia?

A

Yes, ligand substitution occurs.

Cu(H₂O)₄(OH)₂ + 4NH₃ —-> [Cu(H₂O)₂(NH₃)₄]²⁺ + 2H₂O + 2OH⁻

This turns the solution deep blue.

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11
Q

What is the overall reaction for [Cu(H₂O)₆]²⁺ reacting with sodium carbonate?

What colour does this turn?

A

[Cu(H₂O)₆]²⁺ + CO₃²⁻ —-> CuCO₃ + 6H₂O

This forms a green-blue precipitate.

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12
Q

What is the overall reaction for [Fe(H₂O)₆]²⁺ reacting with sodium hydroxide dropwise?

What colour does this turn?

A

[Fe(H₂O)₆]²⁺ + 2OH⁻ —-> Fe(H₂O)₄(OH)₂ + 2H₂O

It forms a green precipitate. This will slowly turn brown in air.

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13
Q

Does [Fe(H₂O)₆]²⁺ react differently in an excess of NaOH?

A

No, it remains the same as dropwise.

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14
Q

What is the overall reaction for [Fe(H₂O)₆]²⁺ reacting with ammonia dropwise?

What colour does this turn?

A

[Fe(H₂O)₆]²⁺ + 2NH₃ —> Fe(H₂O)₄(OH)₂ + 2NH₄⁺

It forms a green precipitate.

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15
Q

Does [Fe(H₂O)₆]²⁺ react differently in an excess of ammonia?

A

No, it is the same as dropwise.

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16
Q

What is the overall reaction for [Fe(H₂O)₆]²⁺ reacting with sodium carbonate?

What colour does this turn?

A

[Fe(H₂O)₆]²⁺ + CO₃²⁻ —-> FeCO₃ + 6H₂O

This forms a green precipitate.

17
Q

What is the overall reaction for [Al(H₂O)₆]³⁺ reacting with sodium hydroxide dropwise?

What colour does this turn?

A

[Al(H₂O)₆]³⁺ + 3OH⁻ —-> Al(H₂O)₃(OH)₃ + 3H₂O

It forms a white precipitate.

18
Q

Does [Al(H₂O)₆]³⁺ react differently in an excess of NaOH?

A

Yes it does. Further hydrolysis occurs.

Al(H₂O)₃(OH)₃ + OH⁻ —-> [Al(H₂O)₂(OH)₄]⁻ + H₂O

The white precipitate redissolves.

19
Q

What is the overall reaction for [Al(H₂O)₆]³⁺ reacting with ammonia dropwise?

What colour does this turn?

A

[Al(H₂O)₆]³⁺ + 3NH₃ —-> Al(H₂O)₃(OH)₃ + 3NH₄⁺

This forms a white precipitate.

20
Q

Does [Al(H₂O)₆]³⁺ react differently in an excess of ammonia?

A

No, it remains the same as dropwise.

21
Q

What is the overall reaction for [Al(H₂O)₆]³⁺ reacting with sodium carbonate?

What colour does this turn?

A

2[Al(H₂O)₆]³⁺ + 3CO₃²⁻ —-> 2Al(H₂O)₃(OH)₃ + 3H₂O + 3CO₂

This forms a white precipitate and bubbles.

22
Q

What is the overall reaction for [Fe(H₂O)₆]³⁺ reacting with sodium hydroxide dropwise?

What colour does this turn?

A

[Fe(H₂O)₆]³⁺ + 3OH⁻ —-> Fe(H₂O)₃(OH)₃ + 3H₂O

It forms a brown precipitate.

23
Q

Does [Fe(H₂O)₆]³⁺ react differently in an excess of NaOH?

A

No, it remains the same as dropwise.

24
Q

What is the overall reaction for [Fe(H₂O)₆]³⁺ reacting with ammonia dropwise?

What colour does this turn?

A

[Fe(H₂O)₆]³⁺ + 3NH₃ —-> Fe(H₂O)₃(OH)₃ + 3NH₄⁺

This forms a brown precipitate.

25
Q

Does [Fe(H₂O)₆]³⁺ react differently in an excess of ammonia?

A

No, it remains the same as dropwise.

26
Q

What is the overall reaction for [Fe(H₂O)₆]³⁺ reacting with sodium carbonate?

What colour does this turn?

A

2[Fe(H₂O)₆]³⁺ + 3CO₃²⁻ —-> 2Fe(H₂O)₃(OH)₃ + 3H₂O + 3CO₂

This forms a brown precipitate and bubbles.

A Level Chemistry (24 decks)

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