Determining the Relative Strengths of Metal Ions as Oxidizing Agents

 

Metals and metal ions are in constant competition for electrons. Some metals lose electrons easily while others do not; conversely, some metal ions gain electrons more easily than others. These competitions form the basis of electrochemistry. Therefore, chemists must know the order of reactivity of the metals and their ions. The following experiment will enable you to prepare a reactivity list for certain metals and their ions.


Purpose

✏ Write the purpose of the activity.


Chemical System

✏ Write the half-reaction equation for the reduction of each of the four metal ions that you will test (see Materials). For example, the half reaction for the reduction of copper(II) ions is . . .

Cu2+(aq) + 2 e– ➞ Cu(s)


Materials

strips of copper, lead, silver, and zinc metals

solutions of copper(II) nitrate, lead(II) nitrate, silver nitrate, and zinc nitrate

steel wool

absorbent paper towel


Procedure

  1.  Clean the metal strips with steel wool.

  2.  Choose one solution and put one drop on each metal strip.

  3.  For each metal, record whether a reaction occurs (a black colour indicated that a reaction has occurred). Allow at least 15 s before concluding that no reaction occurs.

  4.  Repeat steps 2 and 3 for the other solutions.

  5.  Use paper towel to remove the solution drops. Clean the metal strips with steel wool. Return the metal strips.


Observations

Go here to observe the results.

✏ Record the observations in a table similar to table 1.


Table 1: Observations of reactions between metal ions and metals. “YES” means that a reaction occurred. “NO” means that a reaction did not occur.

 

 

Metal

 

 

Cu(s)

Pb(s)

Ag(s)

Zn(s)

Metal

Ion

Cu2+(aq)

—

 

 

 

Pb2+(aq)

 

—

 

 

Ag+(aq)

 

 

—

 

Zn2+(aq)

 

 

 

—


Analysis

✏ Complete the following analysis.

  1.  List the metals from most reactive to least reactive.

  2.  List the metal ions from most reactive to least reactive.

  3.  State a generalization about the relative reactivity of a metal and its ion.

  4.  Construct a “redox table” by arranging the four reduction half-reactions (from the chemical system) in order, starting with the one representing the strongest (most reactive) oxidizing agent and ending with the one representing the weakest (least reactive) oxidizing agent.