Reactions of Ions in Aqueous Solutions

Question 1

What are metal-aqua complexes?
What reaction do they undergo?

Answer 1

transition metal ion is added to water, and coordinate bonds form between them due to the lone pair on O
Hydrolysis

Question 2

What affects the acidity of metal-aqua complexes

Answer 2

charge on the transition metal ion
hydroxonium ions form when water reacts with metal-aqua complexes

Question 3

Which is more acidic: a 3+ metal-aqua complex ion or a 2+ metal-aqua complex ion? Why?

Answer 3

3+ metal-aqua complex ion

-have a higher charge density (high charge and small size)
-hence more polarising (attract electrons in the O-H bond more strongly)
-weakens bond
-more likely that H+ is released

Question 4

What happens during hydrolysis and further hydrolysis of metal-aqua complexes?

Answer 4

Hydrolysis:
-water is added to the metal-aqua complex
-lone pair on O of the added water is attracted to the H on the water ligand
-breaks the O-H bond, forming H3O+ ions

Further hydrolysis:
-an equilibrium is established
-more OH- are added, which react with H3O+
-equilibrium shifts to the right
-continues until insoluble metal hydroxides form (neutral precipitate))

Question 5

Define amphoteric

Answer 5

when metal hydroxides can act as a base or an acid
can be reversed by adding H+ to the metal hydroxide complex
it will dissolve

Question 6

What forms when ammonia reacts with metal-aqua complexes?
What happens when excess ammonia is added?

Answer 6

Metal hydroxides

Ligand substitution

Question 7

What forms when sodium carbonate is added to metal-aqua complexes?

Answer 7

Metal carbonates precipitates