Everything Science Grade 12

CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.4

Example 3: Using the table of Standard Electrode Potentials

QUESTION

Is magnesium able to displace silver from a solution of silver nitrate?

SOLUTION

Step 1 : Determine the half-reactions that would take place if magnesium

were to displace silver nitrate.

The half-reactions are asfollows:

Mg2++ 2e−� Mg

Ag++ e−� Ag

Step 2 : Use the table of electrode potentials to see which metal forms

ions more easily.

For the magnesium half-reaction: E◦V = -2,37. For the silver

half-reaction: E◦V = 0,80.

This means that magnesium is more easily oxidised than sil-

ver and the equilibriumin this half-reaction liesto the left. The

oxidation reaction will occur spontaneously in magnesium. Silver

is more easily reduced and the equilibrium liesto the right in this

half-reaction. It can beconcluded that magnesium will displace

silver from a silver nitrate solution so that there is silver metal and

magnesium ions in the solution.