Chemistry - 3.2.6: Reactions of ions in aqueous solution

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46 Terms

1
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What forms when Fe2+ ions react with water?

[Fe(H2O)6]2+

2
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What forms when Cu2+ ions react with water?

[Cu(H2O)6]2+

3
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What happens when iron (II) complexes are left to stand in air for some time?

Iron (II) ions are oxidised to iron (III) ions, so the colour of any precipitates change from green to brown.

4
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Do further reactions happen when excess ammonia is added to the relevant ions (except Cu)? Why?

Nothing happens - they are insoluble in excess ammonia

5
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What forms when Fe3+ ions react with water?

[Fe(H2O)6]3+

6
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What forms when Al3+ ions react with water?

[Al(H2O)6]3+

7
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Which one is more reactive or acidic - [M(H2O)6]3+ or [M(H2O)6]2+? Why? (3)

[M(H2O)6]3+

  • The 3+ ion has a higher charge/size ratio (is smaller and more highly charged) than the 2+ ion so is more strongly polarising

  • The 3+ ions are more polarising, weakening the O-H bonds

  • The complex then readily releases H+ ions, making the solution more acidic

8
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Aqua ions

Ions that form when the salt of a transition metal is dissolved in water, so the positively charged metal ion is surrounded by (usually 6) water molecules acting as ligands

9
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Write out a hydrolysis reaction

[Fe(H2O)6]3+ + H2O ⇌ [Fe(H2O)5(OH)]2+ + H3O+

10
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What happens when OH- ions are added to an aqua ion?

The ion takes the place of one of the water molecules

11
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How many OH- ions are added in substitution reactions?

The same number as the charge of the metal ion (2 if 2+, 3 if 3+)

12
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What happens when ammonia reacts with aqua ions?

OH- ions are substituted instead of the water molecules - ammonium ions also form

13
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How many ammonia molecules react in substitution reactions?

The same number as the charge of the metal ion (2 if 2+, 3 if 3+)

14
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Why does iron (III) carbonate not exist, while iron (II) carbonate does?

Fe3+ is more acidic than Fe2+, so the carbonate ion can remove protons from the Fe2+ aqua ion but not the Fe3+ aqua ion

15
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What forms in the substitution reaction between 3+ aqua ions and carbonate ions?

M(OH)3(H2O)3 + 1.5CO2 + 1.5H2O

16
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What forms in the substitution reaction between 2+ aqua ions and carbonate ions?

MCO3 + 6H2O

17
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How can you distinguish between [Fe(H2O)6]2+ and [Fe(H2O)6]3+?

By adding dilute alkali - 2+ forms green iron (II) hydroxide, while 3+ forms brown iron (III) hydroxide

18
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Amphoteric

Showing both acidic and basic properties

19
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Why is Al(OH)3(H2O)3 described as amphoteric?

It reacts with acids and bases

20
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Why do aqueous copper ions form a deep-blue colour when excess ammonia is added?

The Cu(OH)2(H2O)4 dissolves in ammonia, forming [Cu(NH3)4(H2O)2]2+

21
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What forms when [Fe(H2O)6]2+ reacts with a few drops of OH-?

Green precipitate of Fe(OH)2(H2O)4

22
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What forms when [Fe(H2O)6]2+ reacts with a excess OH-?

Green precipitate of Fe(OH)2(H2O)4

23
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What forms when [Fe(H2O)6]2+ reacts with a few drops of NH3?

Green precipitate of Fe(OH)2(H2O)4

24
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What forms when [Fe(H2O)6]2+ reacts with excess NH3?

Green precipitate of Fe(OH)2(H2O)4

25
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What forms when [Fe(H2O)6]2+ reacts with CO32-?

Green precipitate of FeCO3

26
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What forms when [Fe(H2O)6]3+ reacts with a few drops of OH-?

Brown precipitate of Fe(OH)3(H2O)3

27
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What forms when [Fe(H2O)6]3+ reacts with excess OH-?

Brown precipitate of Fe(OH)3(H2O)3

28
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What forms when [Fe(H2O)6]3+ reacts with a few drops of NH3?

Brown precipitate of Fe(OH)3(H2O)3

29
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What forms when [Fe(H2O)6]3+ reacts with excess NH3?

Brown precipitate of Fe(OH)3(H2O)3

30
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What forms when [Fe(H2O)6]3+ reacts with CO32-?

Brown precipitate of Fe(OH)3(H2O)3 + bubbles of CO2

31
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What forms when [Al(H2O)6]3+ reacts with CO32-?

White precipitate of Al(OH)3(H2O)3 + bubbles of CO2

32
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What forms when [Al(H2O)6]3+ reacts with a few drops of NH3?

White precipitate of Al(OH)3(H2O)3

33
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What forms when [Al(H2O)6]3+ reacts with excess NH3?

White precipitate of Al(OH)3(H2O)3

34
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What forms when [Al(H2O)6]3+ reacts with a few drops of OH-?

White precipitate of Al(OH)3(H2O)3

35
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What forms when [Al(H2O)6]3+ reacts with excess OH-?

Colourless solution of [Al(OH)4]-

36
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What forms when [Cu(H2O)6]2+ reacts with a few drops of OH-?

Pale blue precipitate of Cu(OH)2(H2O)4

37
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What forms when [Cu(H2O)6]2+ reacts with excess OH-?

Pale blue precipitate of Cu(OH)2(H2O)4

38
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What forms when [Cu(H2O)6]2+ reacts with a few drops of NH3?

Pale blue precipitate of Cu(OH)2(H2O)4

39
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What forms when [Cu(H2O)6]2+ reacts with excess NH3?

Deep blue solution of [Cu(NH3)4(H2O)2]2+

40
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What forms when [Cu(H2O)6]2+ reacts with CO32-?

Blue-green precipitate of CuCO3

41
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Write the ionic equation for the reaction that occurs when Na2CO3 reacts with [Al(H2O)6]

2[Al(G2O)6]3+ + 3CO3 2- → 2Al(OH)3(H2O)3 + 3H2O + 3CO2

42
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What reagent is needed for the conversion of [Fe(H2O)6]3+ to [Fe(H2O)6]2+?

Excess zinc

43
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What forms when [Cu(H2O)6]2+ reacts with excess HCl?

Yellow-green solution of CuCl42-

44
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What pH does a solution of [Al(H2O)6]3+ have? Why?

pH < 7 - Al3+ ion has a high charge density, so it weakens the OH bond

45
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46
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Write an equation to help show why 3+ ions are more acidic than 2+ ions.

[Fe(H2O)6]3+ → [Fe(H2O)5OH]2+ + H+