Ligand Substitution

Question 1

what is ligand substitution?

Answer 1

• one ligand in a complex ion is replaced by another ligand

Question 2

what colour is formed from copper(II) sulfate?

Answer 2

• when copper(II) sulfate dissolves in water, pale blue complex forms
• [Cu(H2O)6]2+

Question 3

what is the equation and colour of [Cu(H2O)6]2+ when excess aqueous ammonia is added?

Answer 3

• [Cu(H2O)6]2+ and NH3(aq) forms a dark blue solution [Cu(NH3)4(H2O)2]2+
• [Cu(H2O)6]2+(aq) + 4NH3(aq) –>[Cu(NH3)4(H2O)2]2+(aq) + 4H2O(l)
• four ammonia ligands are replacing 4 water ligands
• both complexes are octahedral

Question 4

what are the stages of reaction for Cu2+?

Answer 4

[Cu(H2O)6]2+ –> Cu(OH)2 –> [Cu(NH3)4(H2O)2]2+

Question 5

what is the equation and colour of [Cu(H2O)6]2+ when concentrated hydrochloric acid is added?

Answer 5

• pale blue solution forms a yellow solution
• 6 water ligands are placed by 4 chloride ligands
• if water added to yellow solution a blue solution forms
• [Cu(H2O)6]2+(aq) + 4Cl-(aq)
  –> [CuCl4]2- + 6H2O(l)
• ligand changes from octahedral to tetrahedral

Question 6

how is the chromium complex formed?

Answer 6

• KCr(SO4)2.12H2O forms [Cr(H2O)6]3+
• which is a purple solution

Question 7

what is the equation and formula for [Cr(H2O6]3+ and excess aqueous ammonia?

Answer 7

• a pale green precipitate Cr(OH)3 is formed
• Cr(OH)3 dissolves in excess ammonia to form complex ion [Cr(NH3)6]3+
• [Cr(H2O)6]3+(aq) + 6NH3(aq) –> [Cr(NH3)6]3+(aq) + 6H2O(aq)
• colour change from pale purple to purple

Question 8

what is haemoglobin?

Answer 8

• 4 polypeptide chains held together by weak intermolecular bonds
• haemoglobin has a harm group with is Fe2+ which bind to oxygen gas

Question 9

what happens with haemoglobin near the lungs?

Answer 9

• increased concentration of O2(in capillaries of lungs)and decreased concentration of CO2 so Hb binds to oxygen to form oxyhaemoglobin which releases oxygen to body cells when required
• Hb is RBCs bind to CO2 which is carried back to lungs, CO2 is released and exhaled

Question 10

what happens with haemoglobin away from the lungs?

Answer 10

• ## lower concentration of O2 and higher concentration of CO2