Reaction of aqueous ions Flashcards

1
Q

What is the colour of the solution when Cu2+ ions are hydrated to [Cu(H2O)6]2+

A

Blue solution

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2
Q

What is the colour of the solution when Fe2+ ions are hydrated to [Fe(H2O)6]2+

A

Pale green solution

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3
Q

What is the colour of the solution when Fe3+ ions are hydrated to [Fe(H2O)6]3+

A

Yellow brown solution (purple)

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4
Q

What is the colour of the solution when Al3+ ions are hydrated to [Al(H2O)6]3+

A

Colourless solution

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5
Q

Why are Fe3+ and Al3+ ions more acidic than Cu2+ and Fe2+?

A

Fe3+ is smaller and more highly charged than Fe2+
Fe3+ is more polarising
Fe3+ strongly attracts the lone pair on the oxygen of the water ligands
Weakens the O-H bond strength
Fe3+ complexes more easily release H+ ions making the solution acidic
Fe2+ ions do not release H+ ions

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6
Q

Write an equation to show Fe3+ complex act as an acid

A

[Fe(H2O)6]3+ → [Fe(H2O)5(OH)]2+ + H+

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7
Q

Reaction of [Fe(H2O)6]2+ with Na2CO3 equation

A

[Fe(H2O)6]2+ + CO32- —> FeCO3(s) + 6H2O

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8
Q

Observation of [Fe(H2O)6]2+ reacting with Na2CO3

A

Green precipitate

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9
Q

Reaction of [Fe(H2O)6]2+ with NaOH equation

A

[Fe(H2O)6]2+ + 2OH- → Fe(H2O)4(OH2) + 2H2O

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10
Q

Observation of [Fe(H2O)6]2+ with NaOH

A

Green precipitate
(goes brown on standing in air as the oxygen oxidises Fe2+ to Fe3+)

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11
Q

Reaction of [Fe(H2O)6]2+ with NH3 equation

A

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

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12
Q

Observation of [Fe(H2O)6]2+ with NH3

A

Green precipitate
Brown on standing in air

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13
Q

Reaction of [Cu(H2O)6]2+ with Na2CO3 equation

A

[Cu(H2O)6]2+ + CO32- → CuCO3(s) + 6H2O

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14
Q

Observation of [Cu(H2O)6]2+ with Na2CO3

A

Blue-green precipitate

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15
Q

Reaction of [Cu(H2O)6]2+ with NaOH equation

A

[Cu(H2O)6]2+ + 2OH- → Cu(H2O)4(OH)2 + 2H2O

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16
Q

Observation of [Cu(H2O)6]2+ with NaOH

A

Blue precipitate

17
Q

Reaction of [Cu(H2O)6]2+ with NH3 equation

A

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

18
Q

Observation of [Cu(H2O)6]2+ with NH3

A

Blue precipitate

19
Q

Reaction of [Cu(H2O)6]2+ with excess NH3 equation

A

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

20
Q

Observation of [Cu(H2O)6]2+ with excess NH3

A

Deep blue solution

21
Q

Reaction of Cu(H2O)4(OH)2] with excess NH3 equation

A

Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+(aq) + 2H2O + 2OH-

22
Q

Reaction of [Cu(H2O)6]2+ with chloride ions

A

[Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O

23
Q

Observation of [Cu(H2O)6]2+ with chloride ions

A

Yellow solution

24
Q

Reaction of [Fe(H2O)6]3+ with Na2CO3

A

2[Fe(H2O)6]3+ + 3CO32- → 2Fe(H2O)3(OH)3 + 3CO2 + 3H2O

25
Q

Observation of [Fe(H2O)6]3+ with Na2CO3

A

Brown ppt and CO2 gas evolved which gives effervescence

26
Q

Reaction of [Fe(H2O)6]3+ with NaOH

A

[Fe(H2O)6]3+ + 3OH- → Fe(H2O)3(OH)3 + 3H2O

27
Q

Observation of [Fe(H2O)6]3+ with NaOH

A

Brown precipitate

28
Q

Reaction of [Fe(H2O)6]3+ with NH3

A

[Fe(H2O)6]3+ + 3NH3 → Fe(H2O)3(OH)3 + 3NH4+

29
Q

Observation of [Fe(H2O)6]3+ with NH3

A

Brown precipitate

30
Q

Reaction of [Al(H2O)6]3+ with Na2CO3

A

2[Al(H2O)6]3+ + 3CO32- → 2Al(H2O)3(OH)3 + 3CO2 + 3H2O

31
Q

Observation of [Al(H2O)6]3+ with Na2CO3

A

White precipitate and effervescence as CO2
gas evolved

32
Q

Reaction of [Al(H2O)6]3+ with NaOH

A

[Al(H2O)6]3+ + 3OH- → [Al(H2O)3(OH)3] + 3H2O

33
Q

Reaction of [Al(H2O)3(OH)3] with excess NaOH

A

[Al(H2O)3(OH)3] + OH- → [Al(H2O)2(OH)4]- + H2O

34
Q

Observation of [Al(H2O)6]3+ with NaOH

A

White precipitate

35
Q

Observation of [Al(H2O)3(OH)3] with excess NaOH

A

White precipitate dissolves to form a colourless solution

36
Q

Reaction of [Al(H2O)6]3+ with NH3

A

[Al(H2O)6]3+ + 3NH3 → [Al(H2O)3(OH)3] + 3NH4+

37
Q

Observation of [Al(H2O)6]3+ with NH3

A

White precipitate

38
Q

How do Al3+ show amphoteric character?

A

Acting as a base (HCl added):
[Al(H2O)3(OH)3] + 3H+ → [Al(H2O)6]3+
Acting as an acid:
[Al(H2O)3(OH)3] + OH- → [Al(H2O)2(OH)4]- + H2O