Reactions of Aqueous ions

Question 1

Lewis acid

Answer 1

electron pair acceptor

Question 2

Lewis base

Answer 2

electron pair donator

Question 3

Equilibria

Answer 3

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

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

Question 4

Why is 3+ more acidic

Answer 4

3+ metal ions have higher charge density (charge/size ratio) and have greater polarising power. The greater the polarising power, the more strongly it attracts the water molecule. This weakens the O-H bond so it breaks more easily releasing H+ ions.

Question 5

Iron (II)

Answer 5

[Fe(H2O)6]2+(aq)

green solution

Question 6

Copper (II)

Answer 6

[Cu(H2O)6]2+(aq)

blue solution

Question 7

Iron(III)

Answer 7

[Fe(H2O)6]3+(aq)
purple solution

may look yellow- brown due to some [Fe(H2O)5(OH)]2+(aq)

Question 8

Aluminium(III)

Answer 8

[Al(H2O)6]3+(aq)

colourless solution

Question 9

Copper (II) with NaOH

Answer 9

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

Cu(H2O)4(OH)2(s)
blue ppt

Question 10

Aluminium (III) with NaOH

Answer 10

[Al(H2O)6]3+(aq) + 3OH- (aq) -> Al(H2O)3(OH)3 (s) + 3H2O (l)

Al(H2O)3(OH)3(s)
white ppt

Question 11

Iron (III) with NaOH

Answer 11

Fe(H2O)3(OH)3(s)
brown ppt
(ppt may look orange-brown)

Question 12

Iron (II) with NaOH

Answer 12

Fe(H2O)4(OH)2(s)

green ppt goes brown on standing in air

Question 13

Iron (II) Copper (II) Iron (III) with excess NaOH

Answer 13

No further change

Question 14

Aluminium (III) with excess NaOH(aq)

Answer 14

[Al(OH)4]- (aq)
colourless solution

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

Question 15

Iron (II) with NH3(aq)

Answer 15

[Fe(H2O)6]2+ (aq) + 2NH3 (aq) -> Fe(H2O)4(OH)2 (s) + 2NH4+ (aq)

Fe(H2O)4(OH)2(s)
green ppt goes brown on standing in air

Question 16

Iron (III) with NH3(aq)

Answer 16

[Fe(H2O)6]3+ (aq) + 3NH3 (aq) -> Fe(H2O)3(OH)3 (s) + 3NH4+ (aq)

Fe(H2O)3(OH)3(s) brown ppt
(ppt may look orange- brown)

Question 17

Copper (II) with NH3(aq)

Answer 17

Cu(H2O)4(OH)2(s)

blue ppt

Question 18

Aluminium (III) with NH3(aq)

Answer 18

Al(H2O)3(OH)3(s)

white ppt

Question 19

Iron (II) Iron (III) Aluminium (III) with excess NH3 (aq)

Answer 19

No further change

Question 20

Copper (II) with excess NH3(aq)

Answer 20

[Cu(H2O)2(NH3)4]2+(aq)

deep blue solution

Question 21

Iron (II) with Na2CO3(aq)

Answer 21

FeCO3(s)
green ppt

[Fe(H2O)6]2+ +CO32- -> FeCO3+6H2O

Question 22

Copper (II) with Na2CO3(aq)

Answer 22

CuCO3(s)
blue-green ppt

[Cu(H2O)6]2+ + CO32-
->CuCO3+6H2O

Question 23

Iron (III) with Na2CO3(aq)

Answer 23

Fe(H2O)3(OH)3(s)
brown ppt
(ppt may look orange-brown)
and CO2 gas evolved

2[Fe(H2O)6]3+(aq) + 3CO32-(aq)->2Fe(OH)3(H2O)3(s) +3CO2 + 3H2O(l)

Question 24

Aluminium (III) with Na2CO3(aq)

Answer 24

Al(H2O)3(OH)3(s)
white ppt
and CO2 gas evolved

2[Al (H2O)6]3+(aq) + 3CO32-(aq)->2Al(OH)3(H2O)3(s) +3CO2 + 3H2O(l)