Unit 2: Section 4 (part 2) - Reactions of ions in aqueous solution

Question 1

Are 2+ ions or 3+ ions more acidic in solution? Why?

Answer 1

• 3+ ions are much more acidic
• 3+ ions are smaller and more highly charged, so have a higher charge density
• They attract the electrons from the oxygen of the ligands more strongly
• This weakens the O-H bonds, so the complex readily releases a H+ ion into the solution, making it acidic

Question 2

Write an equation for the hydrolysis of a 3+ ion to release a proton

Answer 2

[Fe(H2O)6]^3+(aq) ⇌ [Fe(H2O)5(OH)]^2+(aq) + H+(aq)

Question 3

What kind of acid is the complex ion acting as? Why?
[Fe(H2O)6]^3+(aq) ⇌ [Fe(H2O)5(OH)]^2+(aq) + H+(aq)

Answer 3

Bronsted-Lowry - donates a proton

Question 4

Define a Lewis acid

Answer 4

Electron pair acceptor

Question 5

Define a Lewis base

Answer 5

Electron pair donor

Question 6

What is acting as the Lewis acid and what is acting as the Lewis base during the formation of complex ions?

Answer 6

The metal ion is acting at the Lewis acid and the ligands as Lewis bases