6.2.5 Variable Oxidation States

Question 1

Most common oxidation states of Ti and Ni?

Answer 1

+2 +3 +4

Question 2

Most common oxidation states of V?

Answer 2

+2 +3 +4 +5

Question 3

Most common oxidation states of Cr?

Answer 3

+2 +3 +6

Question 4

Most common oxidation states of Mn?

Answer 4

+2 +4 +6 +7

Question 5

Most common oxidation states of Fe and Co?

Answer 5

+2 +3

Question 6

Most common oxidation states of Cu?

Answer 6

+1 and +2

Question 7

Why do transition metals lose electrons from the 4s subshell first?

Answer 7

• Repulsion between electrons pushes 4s into a higher energy state than 3d subshell
• So electrons in 4s subshell are lost more easily

Question 8

How does pH influence redox potential of a transition metal ion?

Answer 8

• When undergoing change in oxidation states, reactions often involve hydrogen ions
• Lower pH, excess acid, more H+ ions, so ensures reaction goes to completion
• So lower pH causes an increase in oxidation potential

Question 9

How does changing the ligand influence redox potential of a transition metal ion?

Answer 9

• Stronger ligands bind better to central metal atom
• Eg NH3 is a stronger ligand than H2O
• Greater exothermic energy change
• Stronger ligands increase the redox potential

Question 10

In my A level, what is the main reaction which illustrates the variable oxidation states of transition metal ions?

Answer 10

Zinc + Ammonium Vanadate
- Acidic conditions

Question 11

What are the different oxidation states of vanadium + their colours?

Answer 11

Question 12

What are the steps in the full reduction of vanadium by zinc?

Answer 12

Question 13

What is the equation for the reduction of tollen’s reagent?

Answer 13