reactions of metal ions in aq solutions

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Last updated 1:41 PM on 5/21/26
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53 Terms

1
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when anhydrous copper(II) sulphate reacts with water a solution is formed that contains a complex copper (II) ion and sulphate ions. Write an equation

CuSO4  + 6H2O → [Cu(H2O)6]2+ + SO42- 

2
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colour of [Fe(H2O)6]2+ in aqueous solution

green solution

3
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colour of [Cu(H2O)6]2+ in aqueous solution

blue solution

4
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colour of [Co(H2O)6]2+ in aqueous solution

pink solution

5
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colour of [Al(H2O)6]3+ in aqueous solution

colourless solution

6
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colour of [Fe(H2O)6]3+ in aqueous solution

purple solution or yellow/brown/orange solution

7
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Write an equation illustrating [Fe(H2O)6]3+ behaving as an acid. and state colour of each compound

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

purple to yellow/brown

8
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Why is this a hydrolysis reaction?

as the OH bond in a coordinate water molecule is broken into OH- ions and H+ ions. The H+ (aq) ions are released into the solution.

9
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why is it called an acidity reaction?

as hydrolysis leads to the formation of (H3O)+

10
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Two factors that determine the acidity of metal aqua ions

the charge on the metal ion → acidity increases with charge

size of the metal ion → acidity decreases as size increases

11
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Why is a solution of FeCl3 (aq) more acidic than a solution FeCl2(aq) [3]?

M1 Fe3+ is smaller than Fe2+ OR Fe3+ has a greater charge  

M2 Fe3+ ions are more polarizing 

M3 so more O-H bonds in the water ligands break and more H+ ions released  

12
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Explain why the solution containing [Al(H2O)6]3+ is acidic. (2) 

M1 Al3+ has a high charge and small size 

M2 Al3+ weakens the O-H bond in water ligands and donates H+ to water or forms H3O+ ions with water 

13
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The addition of sodium hydroxide results in the addition of hydroxide ions. The addition of hydroxide ions can cause the precipitation of insoluble metal hydroxides. In particular examples the addition of an excess of hydroxide ions can cause the insoluble metal hydroxides to redissolve. 

Why does redissolving happen?

Add OH- to remove the H+ from the equilibrium 

OH- + H+   → H2O 

The equilibrium will shift to the right 

14
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PEQ: write an equation and give observations when 10 drops of NaOH(aq) are  added to a test tube containing CuSO4(aq) (2) 

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

Blue solution Copper (II) hydroxide (blue ppt) 

15
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PEQ: write an equation and give observations when 10 drops of NaOH(aq) are  added to a test tube containing FeSO4(aq) (2) 

[Fe(H2O)6]2+(aq) + 2OH-(aq)    → [Fe(H2O)4(OH)2](s) + 2H2O(l) 

Green solution Iron (II)hydroxide (green ppt) 

16
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If left to stand in air [Fe(H2O)4(OH)2](s) will be oxidised by the oxygen in the air to give a brown precipitate due to the formation of [Fe(H2O)3(OH)3](s)  

Write an equation for this

4Fe(OH)2 + 2H2O  + O2 → 4Fe(OH)3 

17
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PEQ: write an equation and give observations when 10 drops of NaOH(aq) are  added to a test tube containing AlCl3(aq) and state what kind of reaction this is (3)

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

Colourless solution Aluminum (III) hydroxide (white ppt) 

Acid base reaction

18
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PEQ: write an equation and give observations when 10 drops of NaOH(aq) are  added to a test tube containing FeCl3(aq) (2) 

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

Yellow/brown solution         Iron (III) hydroxide (brown ppt) 

19
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Dave added excess dilute ammonia solution to some  [Fe(H2O)6]2+ . He then left the test tube to stand for some time. State and explain what is observed (4)

Green solution of [Fe(H2O)6]2+ would change to a green ppt of [Fe(H2O)4(OH)2] upon addition of NH3(aq).

This green precipitate would react with the oxygen in the air and form a brown ppt of [Fe(H2O)3(OH)3]

20
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Write an equation and state observations when an excess of NaOH is added to Al(OH)3 (2)

[Al(H2O)3(OH)3]
+ OH - → H2O + [Al(H2O)2(OH)4]-1

21
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Observations when NaOH and then excess is added to Fe(H2O)6]2+

green precipitate → will darken due to oxidation

nvr

22
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Observations when NaOH and then excess is added to Cu(H2O)6]2+

[Cu(H2O)4(OH)2] = blue ppt

nvr

23
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Observations when NaOH and then excess is added to Fe(H2O)6]3+

[Fe(H2O)3(OH)3] brown ppt

nvr

24
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Observations when NaOH and then excess is added to Al(H2O)6]3+

[Al(H2O)3(OH)3] = white ppt

redissolves to Gove colourless solution [Al(H2O)2(OH)4]-

25
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[Al(H2O)3(OH)3] is amphoteric

26
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Write an equation illustrating [Al(H2O)3(OH)3] behaving as an acid

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

27
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Write an equation for the reaction of [Al(H2O)3(OH)3](s) with hydroxide ions forming [Al(OH)6]3- observations too. 

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

White precipitate  colourless solution

28
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When reacting with HCl, an acid, [Al(H2O)3(OH)3] is behaving as a… what?

Bronsted Lowry  base. [Al(H2O)3(OH)3]  is accepting protons.

29
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[Al(H2O)3(OH)3](s) + 3HCl (aq) →

[Al(OH)6]3+ + Cl-

30
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An ionic equation of the reaction of [Al(H2O)3(OH)3] with HCl(aq) 

[Al(H2O)3(OH)3](s) + 3H+ (aq) → [Al(OH)6]3+

31
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[Al(H2O)3(OH)3](s) + 3H3O+(aq) →

[Al(H2O)6]3+(aq) + 3H2O(l)

32
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Reactions of [Fe(H2O)6]2+ in solution with ammonia 

[Fe(H2O)4(OH)2]

green ppt

nvr

[Fe(H2​O)6​]2++2NH3​→[Fe(H2​O)4​(OH)2​](s)+2NH4+

33
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Reactions of [Cu(H2O)6]2+ in solution with ammonia 

blue ppt [Cu(H2O)4(OH)2]

deep blue sol [Cu(H2O)2(NH3)4]2+

34
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Reactions of[Fe(H2O)6]3+  in solution with ammonia 

brown ppt [Fe(H2O)3(OH)3]

nvr

35
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Reactions of [Al(H2O)6]3+   in solution with ammonia 

[Al(H2O)3(OH)3] white ppt

nvr

36
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What does the OH- ion cause?

ppt of the insoluble metal hydroxide

37
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Write an equation when NH3 is added dropwise to a solution of CuSO4 (aq) + obsv

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

blue sol to blue ppt

38
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Write an equation when NH3 is added dropwise to a solution of FeSO4 (aq) + obsv

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

39
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Write an equation when NH3 is added dropwise to a solution of FeCl3 (aq) + obsv

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

purple sol to brown ppt

40
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When excess ammonia is added blue ppt of[Cu(H2O)4(OH)2] dissolves. Write a equation of this

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

blue ppt to deep blue sol

41
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write an equation illustrating what is formed when an excess of ammonia is added to an aqueous solution of copper sulphate

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

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

goes to

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

42
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Reactions of [Fe(H2O)6]2+ in aqueous solution with carbonate solution 

green ppt FeCO3

43
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Reactions of [Cu(H2O)6]2+ in aqueous solution with carbonate solution 

blue green ppt CuCO3

44
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Reactions of [Al(H2O)6]3+  in aqueous solution with carbonate solution 

white ppt and fizzing

[Al(H2O)3(OH)3]

45
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Reactions of [Fe(H2O)6]3+  in aqueous solution with carbonate solution 

brown ppt and fizzing

[Fe(H2O)3(OH)3]

46
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Tripositive metal ions are more acidic than the dipositive metal ions.  

e.g. [Fe(H2O)6]3+ is more acidic than  [Fe(H2O)6]2+  why

The Fe3+ ion is smaller and has a greater charge than the Fe2+ metal ions  – it has a have a larger charge:size ratio. This means Fe3+  ion is  more acidic due to the fact they are much more polarising. Fe3+ ions  attracts the electron density from the O atom of the coordinated water molecule to a greater extent than the Fe2+ ion. This means the O-H bond of this molecule is weakened more easily broken by a Fe3+  ion thus more readily releasing H+ to an uncoordinated water molecule.

47
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The reaction of the acidic, tripositive metal aqua ions, with sodium carbonate solution, CO32-, ions results in the evolution of carbon dioxide, effervescence, and the precipitation of the metal hydroxide.   

48
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The general equation is:    

2[M(H2O)6]3+(aq) + 3CO32-(aq) →

2[M(H2O)3(OH)3] (s) + 3CO2 (g) + 3H2O (l) 

49
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[Fe(H2O)6]3+(aq) +     CO32-(aq)   → 

2[Fe(H2O)3(OH)3] (s) + 3CO2 (g) + 3H2O (l) 

purple sol to brown ppt

50
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Carbonate ions reacting with [M(H2O)6]2+ These are examples of acid base reactions. 

The Dipositive metal ions, however do not deprotonate so readily and do not behave as acids in the presence of carbonate ions. Instead they form a precipitate directly with the carbonate ion. No carbon dioxide is evolved. 

51
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The general equation is:  [M(H2O)6]2+(aq) + CO32-(aq) →

MCO3(s) + 6H2O(l) 

52
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Write equations illustrating the reaction of Cu2+ (aq)   ions with aqueous Na2CO3. Observations too please.

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

blue sol to blue green ppt

53
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TM aq ions TEAM effort 1  

Q7. 

An excess of a given reagent is added to each of the following pairs of aqueous metal ions. 

For each metal ion, state the initial colour of the solution and the final observation that you would make. 

In each case, write equation for the formation of the final product from the initial aqueous metal ion. 

(a)     An excess of aqueous sodium carbonate is added to separate aqueous solutions containing [Fe(H2O)6]2+ and [Fe(H2O)6]3+.                 (5) 

(b)     An excess of concentrated hydrochloric acid is added to separate aqueous solutions containing [Cu(H2O)6]2+ and [Co(H2O)6]2+.                (4) 

aqueous solutions containing [Fe(H2O)6]2+ and [Al(H2O)6]3+.   (5) 

(d)     An excess of dilute aqueous ammonia is added to separate aqueous solutions containing [Al(H2O)6]3+ and [Ag(H2O)2]+                            (4) 

answers in booklet