3.2.6 Reactions of aqueous ions

Question 1

Coordinate bond definition

Answer 1

A shared pair of electrons where the electrons have both come from the same atom

Question 2

Ligand definition

Answer 2

An ion or molecule with a lone pair of electrons that can form a coordinate bond with a transition metal ion

Question 3

Complex ion definition

Answer 3

A central atom or ion surrounded by ligands

Question 4

Coordinate number definition

Answer 4

The number of coordinate bonds a transition metal can form

Question 5

Why are the ions called hexa aqua complex ions?

Answer 5

They are surrounded by water

Question 6

What is the colour of the [CU(H2O)6]2+ ion solution?

Answer 6

Blue solution

Question 7

What is the colour of the [Fe(H2O)6]2+ ion solution?

Answer 7

Pale green solution

Question 8

What is the colour of the [Fe(H2O)6]3+ ion solution?

Answer 8

Purple solution, but looks yellow/brown

Question 9

What is the colour of the [Al(H2O)6]3+ ion solution?

Answer 9

Colourless solution

Question 10

What is different about the aluminium ion compared to all the other aqueous ions?

Answer 10

It is not a transition metal, but behaves like one

Question 11

Why is Fe3+ more acidic than Fe2+?

Answer 11

Fe3+ is more highly charged
Fe3+ is more polarising
Fe3+ strongly attracts the lone pair on the oxygen of the water ligand
This weakens the O-H bond strength
The Fe3+ complex more easily releases H+ ions, making the solution more acidic

Question 12

What its the equation that shows Fe3+ acting as an acid?

Answer 12

[Fe(H2O)6]3+ –> [Fe(H2O)5(OH)]2+ + H+

Question 13

Equation of [Fe(H2O)6]2+ reacting with Na2CO3 and the observation

Answer 13

[Fe(H2O)6]2+ + CO3 2- –> FeCO3 + 6H2O
Green solution forms green precipitate

Question 14

Equation of [Fe(H2O)6]2+ reacting with NaOH and the observation

Answer 14

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

Question 15

Equation of [Fe(H2O)6]2+ reacting with NH3 and the observation

Answer 15

[Fe(H2O)6]2+ + 2NH3 –> [Fe(H2O)4(OH)2] + NH4+
Green solution forms green precipitate

Question 16

Equation of [Cu(H2O)6]2+ reacting with Na2CO3 and the observation

Answer 16

[Cu(H2O)6]2+ + CO3 2- –> CuCO3 + 6H2O
Blue solution forms blue precipitate

Question 17

Equation of [Cu(H2O)6]2+ reacting with NaOH and the observation

Answer 17

[Cu(H2O)6]2+ + 2OH- –> [Cu(H2O)4(OH2)] + 2H2O
Blue solution forms blue precipitate

Question 18

Equation of [Cu(H2O)6]2+ reacting with NH3 (dropwise) and the observation

Answer 18

[Cu(H2O)6]2+ + 2NH3 –> [Cu(H2O)4(OH)2] + NH4+
Blue solution forms blue precipitate

Question 19

Equation of [Cu(H2O)6]2+ reacting with excess NH3 and the observation

Answer 19

[Cu(H2O)6]2+ + 4NH3 –> [Cu(H2O)2(NH3)4]2+ +4H2O
Blue precipitate forms dark blue solution

Question 20

Equation of [Fe(H2O)6]3+ reacting with Na2CO3 and the observation

Answer 20

2[Fe(H2O)6]3+ + 3CO3 2- –> 2[Fe(H2O)3(OH)3] + 3CO2 + 3H2O
Yellow brown solution forms brown precipitate and effervescence

Question 21

Equation of [Fe(H2O)6]3+ reacting with NaOH and the observation

Answer 21

[Fe(H2O)6]3+ + 3OH- –> [Fe(H2O)3(OH)3] + 3H2O
Yellow brown solution forms brown precipitate

Question 22

Equation of [Fe(H2O)6]3+ reacting with NH3 and the observation

Answer 22

[Fe(H2O)6]3+ + 3NH3 –> [Fe(H2O)3(OH)3] + 3NH4+
Yellow brown solution forms brown precipitate

Question 23

Equation of [Al(H2O)6]3+ reacting with Na2CO3 and the observation

Answer 23

2[Al(H2O)6]3+ + 3CO3 2- –> 2[Al(H2O)3(OH)3] + 3CO2 +H2O
Colourless solution forms what precipitate and effervescence

Question 24

Equation of [Al(H2O)6]3+ reacting with NaOH and the observation

Answer 24

[Al(H2O)6]3+ + 3OH- –> [Al(H2O)3(OH)3] + 3H2O
Colourless solution forms white precipitate

Question 25

Equation of [Al(H2O)6]3+ reacting with excess NaOH and the observation

Answer 25

[Al(H2O)3(OH)3] + OH- –> [Al(H2O)2(OH)4]- + H2O
White precipitate dissolves to form a colourless solution

Question 26

Equation of [Al(H2O)6]3+ reacting with NH3 and the observation

Answer 26

[Al(H2O)6]3+ + 3NH3 –> [Al(H2O)3(OH)3] + 3NH4+
Colourless solution forms white precipitate

Question 27

Show aluminium hydroxide acting as a base

Answer 27

[Al(H2O)3(OH)3] + 3H+ –> [Al(H2O)6]3+

Question 28

Show aluminium hydroxide acting as an acid

Answer 28

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