Ligand Substitution

Question 1

What do we start off with?

Answer 1

[Co(H₂O)₆]²⁺

Question 2

What is the coordination number of [Co(H₂O)₆]²⁺?

Answer 2

6

Question 3

What is the shape of [Co(H₂O)₆]²⁺?

Answer 3

Octahedral because 6 H2O ligands are bonded to 1 Co2+ ion

Question 4

What colour is [Co(H₂O)₆]²⁺ ?

Answer 4

Pink

Question 5

What reagent is added?

Answer 5

Concentrated HCl

Question 6

How is the reagent added?

Answer 6

Drop by drop

Question 7

Colour change when concentrated HCl is added?

Answer 7

Pale pink solution to blue solution

Question 8

What colour does this appear as and why?

Answer 8

Purple
Because the reaction is equilibrium so a mixture of [Co(H₂O)₆]²⁺ (pink) and [CoCl₄]²⁻ (blue) complexes present give illusion of purple

Question 9

What is formed?

Answer 9

[CoCl₄]²⁻ and substituted 6H2O

Question 10

What colour is [CoCl₄]²⁻ ?

Answer 10

Blue

Question 11

Co ordination number of [CoCl₄]²⁻

Answer 11

4 because 4 dative bonds are formed between ligands and Co2+ ion

Question 12

Does this substitution have a coordination number change and why?

Answer 12

Yes because [Co(H₂O)₆]²⁺ is started with, which has coord number of 6
[CoCl₄]²⁻ is formed which has Coord number of 4

Question 13

Complex we start with

Answer 13

[Co(H₂O)₆]²⁺

Question 16

What is formed

Answer 16

[Co(Cl)4]²-