Transition Metals 15.2

Question 1

Give an example of an acid-base ligand exchange reaction.

Answer 1

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

Question 2

What is an amphoteric substance?

Answer 2

A substance that an can act both as an acid and as a base.

Question 3

What colour is the hexaaquacopper(II) ion and what colour is the tetrachlorocuprate(II) ion?

Answer 3

Blue, yellow. (Green is produced when they are mixed)

Question 4

Give an example of an equation that shows a change in coordination number.

Answer 4

[Cu(H2O)6]^2+ + 4Cl^- [CuCl4]^2- + 6H2O

Question 5

What reaction occurs when sodium hydroxide is added to hexaaquacobalt(II)? What colour changes occur?

Answer 5

[Co(H2O)6]^2+ + 2OH^- –> [Co(H2O)4(OH)2] + H2O

Pink solution forms a blue precipitate.

Question 6

What reaction occurs when concentrated hydrochloric acid is added to hexaaquacobalt(II)? What colour changes occur?

Answer 6

[Co(H2O)6]^2+ + 4Cl^- –> [CoCl4]^2- + 6H2O

Pink solution to blue.

Question 7

Describe how can you show the variable oxidation states of vanadium.

Answer 7

Add zinc to NH4VO3, which contains the VO2^+ ion, in the absence of air. Reduction begins and there is a gradual colour change from yellow, to blue, to green and then to purple, as the oxidation number decreases from +5 to +2.