Inorganic Compound Reactions

Question 1

are 2+ ions or 3+ ions more acidic in solution and why

Answer 1

3+ ions are much more acidic
3+ ions are smaller and more highly charged, so have a higher charge density. they attract the electrons from the oxygen of the ligands much more strongly. this weakens the O-H bonds, so the complex readily releases a H+ ion into the solution, making it acidic

Question 2

what kind of acid is the complex ion acting as? why?
[Fe(H2O)6]3+ <–> [Fe(H2O)5(OH)]2+ + H+

Answer 2

bronsted-lowry - donates a proton

Question 3

define a Lewis acid

Answer 3

electron pair acceptor

Question 4

define a Lewis base

Answer 4

electron pair donor

Question 5

what is acting as the Lewis acid and what is acting as the Lewis base during the formation of complex ions

Answer 5

the metal ion is acting as the Lewis acid and the ligands as Lewis bases

Question 6

complex ion and colour of Fe 2+ in aqueous solution

Answer 6

[Fe(H2O)^]2+ (aq)
green

Question 7

complex ion and colour of Fe 2+ when adding NaOH (dropwise and excess)

Answer 7

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

Question 8

complex ion and colour of Fe 2+ when adding NH3 (dropwise and excess)

Answer 8

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

Question 9

complex ion and colour of Fe 2+ when adding Na2CO3

Answer 9

FeCO3
green ppt

Question 10

why does the green ppt go brown on standing in air in the reaction of Fe 2+ with NH3

Answer 10

oxygen in the air oxidises Fe 2+ to Fe 3+, and [Fe(OH)3(H2O)3] is brown, so colour changes

Question 11

complex ion and colour of Cu 2+ in aqueous solution

Answer 11

[Cu(H2O)6] 2+
blue

Question 12

complex ion and colour of Cu 2+ when adding NaOH (dropwise and excess)

Answer 12

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

Question 13

complex ion and colour of Cu 2+ when adding NH3 dropwise

Answer 13

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

Question 14

complex ion and colour of Cu 2+ when adding NH3 excess

Answer 14

[Cu(H2O)2(NH3)4] 2+ (aq)
deep blue solution

Question 15

complex ion and colour of Cu 2+ add Na2CO3

Answer 15

CuCO3
blue-green ppt

Question 16

complex ion and colour of Cu 2+ when adding concentrated HCl

Answer 16

[CuCl4] 2- (aq)
pale green/yellow solution

Question 17

complex ion and colour of Fe 3+ in aqueous solution

Answer 17

[Fe(H2O)6]3+
purple solution, may look yellow-brown due to [Fe(H2O)5(OH)] 2+ (aq)

Question 18

complex ion and colour of Fe 3+ add NaOH (dropwise and excess)

Answer 18

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

Question 19

complex ion and colour of Fe 3+ add NH3 (dropwise and excess)

Answer 19

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

Question 20

complex ion and colour of Fe 3+ add Na2CO3

Answer 20

[Fe(H2O)3(OH3)] (s)
brown ppt, may look orange-brown, effervescence

Question 21

complex ion and colour of Al 3+ in aqueous solution

Answer 21

[Al(H2O)6] 3+
colourless

Question 22

complex ion and colour of Al 3+ add NaOH (dropwise)

Answer 22

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

Question 23

complex ion and colour of Al 3+ add NaOH (excess)

Answer 23

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

Question 24

complex ion and colour of Al 3+ when adding NH3 (dropwise and excess)

Answer 24

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

Question 25

complex ion and colour of Al 3+ when adding Na2CO3

Answer 25

[Al(H2O)3(OH)3] (s)
white ppt and effervescence

Question 26

complex ion and colour of Co 2+ in aqueous solution

Answer 26

[Co(H2O)6] 2+
pink

Question 27

complex ion and colour of Co 2+ when adding NaOH (dropwise and excess)

Answer 27

[Co(H2O)4(OH)2] (s)
blue ppt

Question 28

complex ion and colour of Co 2+ when adding NH3 (dropwise and excess)

Answer 28

[Co(NH3)6] 2+ (aq)
pale brown solution

Question 29

complex ion and colour of Co 2+ when adding Na2CO3

Answer 29

CoCO3 (s)
purple ppt

Question 30

complex ion and colour of Co 2+ when adding HCl

Answer 30

[CoCl4] 2- (aq)
blue solution