A-Level Chemistry (AQA) > 3.2.6 Ions in aqueous solution > Flashcards

3.2.6 Ions in aqueous solution Flashcards

Analyse aqueous metal ion reactions by predicting hydrolysis, precipitation, and ligand exchange outcomes. (39 cards)

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1
Q

What type of ion is formed when transition metal ions dissolve in water?

A

Metal-aqua ion

Water molecules act as ligands forming complexes such as [M(H2O)6]2+.

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2
Q

What ligand surrounds metal ions in aqueous transition-metal complexes?

A

Water

Six water molecules usually coordinate to the metal ion.

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3
Q

Fill in the blank:

The complex ion formed when Fe2+ dissolves in water is Fe(H2O)6.

A

2+

This is an octahedral metal-aqua complex.

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4
Q

True or False:

The acidity of [M(H2O)6]3+ ions is greater than that of [M(H2O)6]2+ ions.

A

True

Higher charge density polarises the O–H bonds more strongly.

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5
Q

What property explains why [M(H2O)6]3+ ions are more acidic than [M(H2O)6]2+ ions?

A

Higher charge density

Greater charge/size ratio weakens O–H bonds in coordinated water.

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6
Q

True or False:

Aluminium hydroxide dissolves in both acids and bases.

A

True

This demonstrates amphoteric behaviour.

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7
Q

Fill in the blank:

A substance that reacts with both acids and bases is described as _______.

A

amphoteric

Examples include Al(OH)3.

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8
Q

What reagent forms a blue precipitate with Cu2+ ions in solution?

A

Sodium hydroxide

Cu2+ forms a blue Cu(OH)2 precipitate.

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9
Q

True or False:

Fe2+ ions form a green precipitate when reacting with hydroxide ions.

A

True

Fe(OH)2 appears green but turns brown when oxidised.

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10
Q

Fill in the blank:

Fe3+ ions react with hydroxide ions to form a _______ precipitate.

A

brown

The precipitate formed is Fe(OH)3.

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11
Q

What reagent can dissolve aluminium hydroxide precipitate to form a colourless solution?

A

Excess sodium hydroxide

The amphoteric hydroxide dissolves forming a complex ion.

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12
Q

What laboratory method uses these reactions to identify transition metal ions?

A

Test-tube reactions

Observing colour changes and precipitates helps identify ions.

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13
Q

What is the colour of [Fe(H₂O)₆]²⁺(aq)?

A

Green solution

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14
Q

What is the colour of [Cu(H₂O)₆]²⁺(aq)?

A

Blue solution

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15
Q

What is the colour of [Fe(H₂O)₆]³⁺(aq)?

A

Pale violet solution

Appears orange due to hydrolysis.

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16
Q

What is the colour of [Al(H₂O)₆]³⁺(aq)?

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A

Colourless solution

17
Q

What happens when NaOH(aq) is added dropwise to [Fe(H₂O)₆]²⁺(aq)?

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A

[Fe(H₂O)₄(OH)₂] forms

Green precipitate, darkens on standing due to oxidation to [Fe(H₂O)₃(OH)₃].

18
Q

What happens when NaOH(aq) is added dropwise to [Cu(H₂O)₆]²⁺(aq)?

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A

[Cu(H₂O)₄(OH)₂] forms

Blue precipitate.

19
Q

What happens when NaOH(aq) is added dropwise to [Al(H₂O)₆]³⁺(aq)?

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A

[Al(H₂O)₃(OH)₃] forms

White precipitate.

20
Q

What happens when NaOH(aq) is added dropwise to [Fe(H₂O)₆]³⁺(aq)?

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A

[Fe(H₂O)₃(OH)₃] forms

Brown precipitate.

21
Q

What happens when excess NaOH(aq) is added to [Fe(H₂O)₆]²⁺(aq)?

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A

No further reaction

22
Q

What happens when excess NaOH(aq) is added to [Cu(H₂O)₆]²⁺(aq)?

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A

No further reaction

23
Q

What happens when excess NaOH(aq) is added to [Fe(H₂O)₆]³⁺(aq)?

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A

No further reaction

24
Q

What happens when NH₃(aq) is added dropwise to [Fe(H₂O)₆]²⁺(aq)?

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A

[Fe(H₂O)₄(OH)₂] forms

Green precipitate, darkens on standing.

25
What happens when **NH₃(aq)** is added **dropwise** to **[Cu(H₂O)₆]²⁺(aq)**?
[Cu(H₂O)₄(OH)₂] forms ## Footnote Blue precipitate.
26
What happens when **NH₃(aq)** is added **dropwise** to **[Fe(H₂O)₆]³⁺(aq)**?
[Fe(H₂O)₃(OH)₃] forms ## Footnote Brown precipitate.
27
What happens when **NH₃(aq)** is added **dropwise** to **[Al(H₂O)₆]³⁺(aq)**?
[Al(H₂O)₃(OH)₃] forms ## Footnote White precipitate.
28
What happens when **excess NH₃(aq)** is added to **[Fe(H₂O)₆]²⁺(aq)**?
No further reaction
29
What happens when **excess NH₃(aq)** is added to **[Cu(H₂O)₆]²⁺(aq)**?
[Cu(H₂O)₂(NH₃)₄]²⁺ forms ## Footnote Deep blue solution.
30
What happens when **excess NH₃(aq)** is added to **[Fe(H₂O)₆]³⁺(aq)**?
No further reaction
31
What happens when **excess NH₃(aq)** is added to **[Al(H₂O)₆]³⁺(aq)**?
No further reaction
32
What happens when **Na₂CO₃(aq)** is added to **[Fe(H₂O)₆]²⁺(aq)**?
FeCO₃ forms ## Footnote Green precipitate.
33
What happens when **Na₂CO₃(aq) is added to [Cu(H₂O)₆]²⁺(aq)**?
CuCO₃ forms ## Footnote Blue-green precipitate.
34
What happens when **Na₂CO₃(aq) is added to [Fe(H₂O)₆]³⁺(aq)**?
[Fe(H₂O)₃(OH)₃] forms + CO₂ gas (brown precipitate & bubbles) ## Footnote Brown precipitate & bubbles.
35
What happens when **Na₂CO₃(aq)** is added to **[Al(H₂O)₆]³⁺(aq)**?
[Al(H₂O)₃(OH)₃] forms + CO₂ gas ## Footnote White precipitate & bubbles.
36
Why do [Fe(H₂O)₆]³⁺ and [Al(H₂O)₆]³⁺ form **hydroxides with CO₃²⁻**?
High charge density polarises CO₃²⁻ leading to hydrolysis → CO₂ + OH⁻ formed → hydroxide precipitate
37
Why does **[Al(H₂O)₃(OH)₃] dissolve in excess NaOH**?
It is amphoteric and forms [Al(H₂O)₂(OH)₄]⁻
38
Why does **[Cu(H₂O)₆]²⁺ form a deep blue solution in excess NH₃**?
Ligand substitution forms [Cu(H₂O)₂(NH₃)₄]²⁺
39
Why does **[Fe(H₂O)₄(OH)₂] darken on standing**?
It is oxidised to [Fe(H₂O)₃(OH)₃] by oxygen in air.
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