ligand substitution

Question 1

what is ligand substitution?

Answer 1

some ligands combine more strongly than others with a transition metal ion
- a ligand that binds more stronglywill displace a metal that binds more weakly
- forming different coloured compounds

Question 2

What happens when ammonia is added to [Cu(H20)6]2+ ?
Include the chemical equation and colour changes.

Answer 2

[Cu(H2O)6]2+ + 4NH3 => [Cu(NH3)4(H2O)2]2+ + 4H2O
Colour Change:
[Cu(H2O)6]2+ is pale blue
[Cu(NH3)4(H2O)2]2 is deep blue
- dropwise = pale blue ppt of Cu(OH)2

Question 3

Describe the reaction when concentrated HCl is added to [Cu(H2O)6]2+ ?
Include the chemical equation and colour changes.

Answer 3

[Cu(H2O)6]2+ + 4Cl => [CuCl4]2- + 6H2O
[Cu(H2O)6]2+ is pale blue
[CuCl4]2- is green inititally then yellow

Question 4

Describe the reaction when ammonia is added to [Cr(H2O)6]3+

Answer 4

[Cr(H2O)6]3+ + 6NH3 => [Cr(NH3)6]3+ + 6H20
[Cr(H2O)]3+ is violet or grey-green
[Cr(NH3)6]3+ is violet

Question 5

describe the ligand substitution of haemoglobin

Answer 5

• O2 binds to Fe2+
• haem groups pick up O2 at the lungs and release it when it passes cells
• the O2 undergoes lignad substitution with H2O in areas of low oxygen conc
• CO can also bind much more strongly to Fe2+ in haem group - ireversible