Reactions of Ions A2

Question 1

Why is an Fe3+ complex more acidic than an Fe2+ complex

Answer 1

Fe3+ is smaller and has a higher charge, so a larger charge density. This attracts electrons from the oxygen in water ligands and weakens the OH bond, allowing for H+ to be released

Question 2

What occurs when a base is added to an complex

Answer 2

2/3 of the H2O is turned into OH- (base takes H+ from H2O), leaving a complex with no charge forming a precipitate

Question 3

Why is there an Fe(II) carbonate but no Fe(III) carbonate

Answer 3

The carbonate can remove protons from an Fe3+ complex but cannot do the same with an Fe2+ complex (Fe3+ more acidic)

Question 4

What does amphoteric mean

Answer 4

Shows both acidic and basic properties

Question 5

What is an example of an amphoteric hydroxide

Answer 5

Al(H2O)3(OH)3

Question 6

What is chelation

Answer 6

When the number of ligands bonded to a complex decreases due to a ligand substituting for a bidentate or a multidentate

Question 7

Why is chelation energetically favourable

Answer 7

Increase in entropy as more product moles than reactants

Question 8

What is an example of a multidentate

Answer 8

EDTA4-

Question 9

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

Answer 9

Pale green

Question 10

What is the colour of [Cu(H2O)6]2+

Answer 10

Pale blue

Question 11

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

Answer 11

Pale yellow

Question 12

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

Answer 12

Colourless

Question 13

What occurs when OH- is added to [Fe(H2O)6]2+

Answer 13

Deprotonated twice to form [Fe(H2O)4(OH)2]. No difference after excess added

Question 14

What is the colour of [Fe(H2O)4(OH)2]

Answer 14

Green gelatinous precipitate

Question 15

What occurs when NH3 is added to [Fe(H2O)6]2+

Answer 15

Deprotonated twice to form [Fe(H2O)4(OH)2]. No difference after excess added

Question 16

What occurs when (CO3)2- is added to [Fe(H2O)6]2+

Answer 16

Green precipitate of FeCO3 is formed

Question 17

What occurs when OH- is added to [Cu(H2O)6]2+

Answer 17

Deprotonated twice to form [Cu(H2O)4(OH)2]. No difference after excess added

Question 18

What is the colour of [Cu(H2O)4(OH)2]

Answer 18

Pale blue precipitate

Question 19

What occurs when NH3 is added to [Cu(H2O)6]2+

Answer 19

Little NH3 deprotonated twice. Excess NH3 does partial ligand substitution to form [Cu(NH3)4(H2O)2]2+

Question 20

What is the colour of [Cu(NH3)4(H2O)2]2+

Answer 20

Deep blue solution

Question 21

What occurs when (CO3)2- is added to [Cu(H2O)6]2+

Answer 21

Blue-green precipitate of CuCO3 is formed

Question 22

What happens to [Fe(H2O)4(OH)2] after some time

Answer 22

Soon oxidises by air to brown [Fe(H2O)3(OH)3]

Question 23

What occurs when OH- is added to [Fe(H2O)6]3+

Answer 23

Deprotonated thrice to form [Fe(H2O)3(OH)3]. No change in excess

Question 24

What is the colour of [Fe(H2O)3(OH)3]

Answer 24

Brown gelatinous precipitate

Question 25

What occurs when NH3 is added to [Fe(H2O)6]3+

Answer 25

Deprotonated thrice to form [Fe(H2O)3(OH)3]. No change in excess

Question 26

What occurs when (CO3)2- is added to [Fe(H2O)6]3+

Answer 26

Deprotonated thrice to form [Fe(H2O)3(OH)3] and bubbles of CO2

Question 27

What occurs when OH- is added to [Al(H2O)6]3+

Answer 27

Little OH- deprotonated to form [Al(H2O)3(OH)3]. Excess OH- forms [Al(OH)4]-]

Question 28

What is the colour of [Al(H2O)3(OH)3]

Answer 28

White precipitate

Question 29

What is the colour of [Al(OH)4]-]

Answer 29

Colourless solution as it’s charged

Question 30

What occurs when NH3 is added to [Al(H2O)6]3+

Answer 30

Deprotonated thrice to form [Al(H2O)3(OH)3]. No change in excess

Question 31

What occurs when (CO3)2- is added to [Al(H2O)6]3+

Answer 31

Deprotonated thrice to form [Al(H2O)3(OH)3] and bubbles of CO2