Reactions of Ions in Aquoeus Solution

Question 1

lewis acid

Answer 1

electron pairacceptor

Question 2

lewis base

Answer 2

electron pair donor.

Question 3

what does the igand in the formation of complex ions act as and why

Answer 3

the ligand acts as a lewis base as it donates the elctrons in the dative covalent bond and the metal is the lewis acid.

Question 4

what are metal aqua ions

Answer 4

transition metals in water. the water moolecules form 6 co-ordinate bonds with the metal ion, which forms the complex ions.

Question 5

what is [M(H2O)6]^2+ limited to

Answer 5

Fe (II) = green
Cu = blue

Question 6

what is [M(H2O)6]^3+ limited to

Answer 6

Al = colourless
Fe (III) = violet.

Question 7

why does the Fe(III) appear yellow/brown in solution. and when does it appear violet.

Answer 7

cos of a hydrolysis reaction that happens in the solution with Fe(III).
it only appears violet in solid hydrated salts that contain these complexes.

Question 8

why does the Fe(III) appear yellow/brown in solution. and when does it appear violet.

Answer 8

cos of a hydrolysis reaction that happens in the solution with Fe(III).
it only appears violet in solid hydrated salts that contain these complexes.

Question 9

Give the equation of when [M(H2O)6]^2+ and [M(H2O)6]^3+ are reacted with water (so in aqueous solutions)

Answer 9

[M(H2O)6]2+ + H2O <—> [M(H2O)5(OH)]^+ + H3O+

[M(H2O)6]3+ + H2O <—> [M(H2O)5(OH)]^2+ + H3O+

the equilibria leads to the the M3+ ion solutions being noticeably more acidic and the M2+ ion solutions being weakly acidic.

Question 10

why are M3+ ion solutions more acidic then the M2+ ions

Answer 10

3+ metals ions have a higher charge density and have greater polarizing power. the greater polarizing power, the more strongly it attracts the water molecule. this weakens the O-H bond so it breaks more easily releasing H+ ions.

Question 11

what is the reaction that happens with limited OH- /limited NH3 with metal aqua ions

Answer 11

its a deprotonation acid base reaction. and it forms insoluble metal hydroxides.

Question 12

give the colour of the ppt formed when the insoluble metal hydroxides = M(OH)2(H2O)4 (s)are formed with Cu, Fe(II) (the 2+ metal ions)

Answer 12

Cu = blue ppt.
Fe (II) = green ppt.

Question 13

give the colour of the ppt formed when the insoluble metal hydroxides = M(OH)2(H2O)3 (s)are formed with Al, Fe(II) (the 3+ metal ions)

Answer 13

Al = white ppt
Fe(III) = brown ppt.

Question 14

what ahappens when metal aqua ions are added OH- ions to produce neutral & insoluble metal hydroxides. (for example with 3+ metal ions and 2+ metal ions)

Answer 14

• First water with 3+ metal-aqua ions like Al3+ and Fe3+. They are hydrolysed and establish an equilibrium:
  M(H2O)6^3+(aq) + H20(l) <—> [M(OH)(H20)5]^2+(aq) + H30^+(aq)
• Further hydrolysis = adding OH- ions then removes H3O+ and the equiibrium shifts to the right, this establishes an new equilibirium in the solution.
  [M(OH)(H20)5]^2+ (aq) + H20(l) <—> [M(OH)(H20)4]^+(aq) + H30^+(aq)
• Finally further hydrolysis shifts the equilibrium more to the right.
  [M(OH)(H20)4]^+(aq) + H20(l) <—> M(OH)(H20)3 (aq) + H30^+(aq)
• this leaves us with an insoluble and uncharged metal hydroxide.
• the same thing happens with metal 2+ ions (like Fe(II) and Cu, but there are only 2 steps cos only 2 of the ligands need to be deprotonated to make the 2+ complex uncharged (=neutral) and so unsoluble.

Question 15

write the whole equations for
1. [Cu(H2O)6]^2+ (aq) with OH- ions
2. [Al(H2O)6]^3+ (aq) with OH- ions

Answer 15

1. [Cu(H2O)6]2+(aq) + 2OH-(aq) -> Cu(H2O)4(OH)2 (s) + 2H2O (l)
2. [Al(H2O)6]3+(aq) + 3OH-(aq) -> Al(H2O)3(OH)3 (s) + 3H2O (l)