Activity:

Single Displacement and Double Displacement Reactions

Introduction:

Single Displacement Reactions

Single displacement reactions are those in which one element reacts with a compound to replace one of the ions in that compound. Two types of reactions are possible:

A metal with a strong tendency to lose electrons can replace a metal ion from a compound in solution. The stronger a metal's tendency to lose electrons, the more reactive it is said to be. The general equation for this reaction is:

A + BC --> AC + B where: A and B are both metals, and C is a non-metal

Just like a girl would never leave her boyfriend for another guy, unless the other guy was better looking; the lone metal can only displace the metal in the compound if the lone metal is more reactive.

The second less common type of single displacement reaction, involves the replacement of a negative, non-metal ion in a compound by a lone non-metal with a greater tendency to gain electrons. The stronger a non-metal's tendency to gain electrons, the more reactive it is said to be. The general equation for this reaction is:

D + EF --> ED + F where: E is a metal, and both D and F are non-metals

Just like a boy would never leave his girlfriend for another girl unless, the other girl was more intelligent; the lone non-metal can only displace the non-metal in the compound if the lone non- metal is more reactive.

Single displacement reactions are used to remove metal ions from industrial effluent. They are also used in household cleaners for metals like copper, silver, and brass.

Double Displacement Reactions

Double displacement reactions are those in which the ions in the solutions of two compounds switch to form two new compounds. These reactions will only occur if one of the new compounds formed is not soluble in water. The general for this reaction is:

AB + CD --> AD + CB where: A and C are metals and B and D are non-metals

For this reaction to occur, one of AD or CB must be insoluble in water.

These reactions are also used to remove ions from waste water before it is released back into the environment.

Purpose: to observe a single displacement reaction and a double displacement reaction

Materials: Copper(II) sulphate solution 1 regular test tube

Aluminum foil 2 tiny test tubes

Potassium iodide solution Safety Goggles

Lead(II) nitrate solution

Safety: Lead solutions can transfer lead into your fat tissues where the lead will remain for the rest of your life!!! If the lead concentrations in your body become high enough your mental processes will slow down!

Do not touch the lead solutions.

Dispose of all lead waste in the container provided.

Procedure:

1. Single Displacement

Pour enough Copper(II) sulphate solution into a test tube from your lab station to cover two fingers. Obtain a small piece of aluminum foil and make it into a tiny ball. Drop the ball into your test tube of Copper(II) sulphate solution. Observe. If nothing happens, continue on to part 2 and look at your aluminum foil ball again later.

2. Double Displacement

Obtain two tiny test tubes. Use an eyedropper to transfer about a quarter of a test tube of Potassium iodide solution into the first test tube and use a second eyedropper to transfer about a quarter of a test tube of Lead(II) nitrate solution into the second test tube. Bring the test tubes to your lab station.

Do not spill the Lead(II) nitrate solution.

Pour the contents of one test tube into the other. Observe.

Dispose of the products in the waste container provided.

Observations:

Single Displacement

Double Displacement

Conclusions:

Write word equations for the two reactions you just observed.