3.2.6 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 much 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 hyrdolysis of a 3+ ion to release a proton.

Answer 2

Question 3

What kind of acid is the complex ion acting as? Why?

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 as the Lewis acid and the ligands are acting as the Lewis base

Question 7

Fill in the table for Fe²⁺

Answer 7

Question 8

Why does the green ppt go brown on standing in air in the reaction of Fe²⁺ with NH₃?

Answer 8

Oxygen in the air oxidises Fe²⁺ to Fe³⁺, and [Fe(OH)₃(H₂O)₃] is brown, so colour changes

Question 9

Fill in the table for the reactions of Cu²⁺

Answer 9

Question 10

Fill in the table for the reactions of Fe³⁺

Answer 10

Question 11

Fill in the table for the reactions of Al³⁺

Answer 11

Question 12

Fill in the table for the reactions of Co²⁺

Answer 12