Reactions of transition metal ions in aqueous solution

Question 1

Name the formula formed when added to (aq) with Fe/Cu

Answer 1

[M(H2O)6]2+

Question 2

Name the formula formed when added to (aq) with Al/Fe

Answer 2

[M(H2O)6]3+

Question 3

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

Answer 3

blue

Question 4

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

Answer 4

pale green

Question 5

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

Answer 5

yellow

Question 6

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

Answer 6

colourless

Question 7

What happens when metal hexa aqua ions react with NaOH?

Answer 7

-a little/a few drops of NaOH, all form a metal hydrogen precipitate
-with excess, only [Al(OH)3(H2O)3] dissolves to make a colourless solution

Question 8

What is the equation for NaOH and [M(H2O)6]2+?

Answer 8

[M(H2O)6]2+ (aq) + 2OH- (aq) –> M(OH)2(H2O)4 + 2H2O(l)

Question 9

What colour is Cu(OH)2(H2O)4?

Answer 9

blue precipitate

Question 10

What colour is Fe (OH)2(H2O)4?

Answer 10

green precipitate

Question 11

What is the equation for NaOH and [M(H2O)6]3+?

Answer 11

[M(H2O)6]3+ (aq) + 3OH- (aq) –> M(OH)3(H2O)3 + 3H2O(l)

Question 12

What colour is Fe(OH)3(H2O)3?

Answer 12

brown precipitate

Question 13

What colour is Al(OH)3(H2O)3?

Answer 13

white precipitate - dissolves in excess NaOH to form a colourless solution

Question 14

What is the equation for excess NaOH and AlCl3?

Answer 14

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

Question 15

What happens when metal hexa aqua ions react with NH3?

Answer 15

-all form precipitates with a little/few drops of ammonia
-with excess, only Cu2+ forms a complex containing NH3

Question 16

What is the equation for NH3 and [M(H2O)6]2+?

Answer 16

[M(H2O)6]2+ (aq) + 2NH3(aq) –> [M(OH)2(H2O)4] (s) + 2NH4+ (aq)

Question 17

What is the equation for NH3 and [M(H2O)6]3+?

Answer 17

[M(H2O)6]3+ (aq) + 3NH3(aq) –> [M(OH)3(H2O)3] (s) + 3NH4+ (aq)

Question 18

What is the equation for [Cu(OH)2(H2O)4] (s) and excess ammonia?

Answer 18

[Cu(OH)2(H2O)4] (s) + 4NH3 (aq) –> [Cu(NH3)4(H2O)2]2+ (aq) + 2OH- (aq) + 2H2O(l)

partial ligand substitution

Question 19

How can you determine the charge on a metal ion?

Answer 19

-adding Na2CO3(aq)
-all the M2+ form metal(II) carbonate precipitate, NO FIZZING/NO CO2 - not acidic enough to convert it to CO2
-all the M3+ form metal(III) hydroxide precipitate, FIZZING/CO2 GAS

Question 20

What is the equation for M2+ and Na2CO3?

Answer 20

[M(H2O)6]2+ (aq) + CO3 2- –> MCO3(s) + 6H2O(l)

Question 21

What colour is [Cu(NH3)4(H2O)2]2+ (aq)?

Answer 21

deep blue

Question 22

What is the equation for M3+ and Na2CO3?

Answer 22

[M(H2O)6]3+ (aq) + 3CO3 2- –> 2M(OH)3(H2O)3 + 3CO2(g) + 3H2O(l)

Question 23

[Cu(H2O)6]2+ (aq) + 4Cl- –>

blue

Answer 23

[CuCl4]2- + 6H2O (l)

yellow-green solution

Question 24

[Fe(H2O)6]2+ (aq) + 4Cl- –>

pale green

Answer 24

[FeCl4]2- + 6H2O (l)

green solution

Question 25

[Fe(H2O)6]3+ (aq) + 4Cl- –>

yellow

Answer 25

[FeCl4]- + 6H2O (l)

yellow

Question 26

[Al(H2O)6]3+ (aq) + 4Cl- –>

colourless

Answer 26

[AlCl4]- + 6H2O (l)

colourless

Question 27

What is special about Al(OH)3(H2O)3 ?

Answer 27

amphoteric - dissolves in both acids and alkalis

Question 28

Why is M3+ more acidic than M2+?

Answer 28

-the M3+ ion is both smaller and more highly charged than the M2+ ion (it has a higher charge/size ratio)
-so is more strongly polarising
-the M3+ ion attracts electrons more strongly from the oxygen atoms of the water ligands, so weakens the O-H bonds in the water molecules more
-which releases more H+ ions, increasing [H+], making the solution more acidic

Question 29

Use equations to show why is M3+ more acidic than M2+

Answer 29

[M(H2O)6]2+ (aq) + H2O(l) ⇌ [M(OH)(H2O)5]+ (aq) + H3O+ (aq)

[M(H2O)6]3+ (aq) + H2O(l) ⇌ [M(OH)2(H2O)5]2+ (aq) + H3O+ (aq)

Question 30

How is VO2+ produced?

Answer 30

VO3- + 2H+ ⇌ VO2+ + H2O
orange ———yellow
acid-base, not redox

Question 31

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

Answer 31

purple

Question 32

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

Answer 32

green

Question 33

What is the colour of [VO(H2O)5]2+?

Answer 33

blue

Question 34

What is the colour of [VO2(H2O)4]+?

Answer 34

yellow