2.6 Aqueous Ions

Question 1

Define the coordination number

Answer 1

number of coordinate bonds a transition metal forms

Question 2

Define a ligand

Answer 2

an ion or molecule with a lone pair of electrons which can form a coordinate bond with a metal ion.

Question 3

Colours of the complex ions

Answer 3

[Cu(H2O)6]^2+ : blue solution
[Fe(H2O)6]^2+ :
Pale green solution
[Fe(H2O)6]^3+ :
yellow brown solution
[Al(H2O)6]^3+ :
colourless solution

Question 4

Why is Fe^3+ more acidic than Fe^2+

Answer 4

*Fe^3+ is smaller and has a higher charge
*So Fe^3+ is more polarising
*Fe^3+ more strongly attracts the lone pair on the oxygen of the water ligands
*It weakens the O-H bond strength
Fe(III) complex more easily releases H^+ ions making the solution more acidic

Question 5

Reactions of [Fe(H2O)6]^2+
with
Na2CO3
NaOH
NH3
state equation and observation

Answer 5

Na2CO3
[Fe(H2O)6]2+ + CO32- -> FeCO3(s) + 6H2O
Green solution -> green precipitate

NaOH
[Fe(H2O)6]2+ + 2OH- -> [Fe(H2O)4(OH)2] + 2H2O
Green solution -> green precipitate

NH3
[Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+
Observation: Green solution -> green precipitate

Question 6

Reactions of [Cu(H2O)6]^2+ with
Na2CO3
NaOH
NH3
Give observations and equations

Answer 6

Question 7

Reaction when [Cu(H2O)6]^2+ reacts with HCl

Answer 7

Question 8

Reactions of [Fe(H2O)6]^3+ with
Na2CO3
NaOH
NH3
Give observations and equations

Answer 8

Question 9

Reactions of [Al(H2O)6]3^+ with
Na2CO3
NaOH
NH3

Answer 9

Question 10

Answer 10