Double Replacement Reactions

Double Replacement Reaction

Background Information:

What Is a Double Replacement Reaction?

Imagine going to a dance and having a dance partner. Once you arrive to the dance, you interact with other people and you end up switching dance partners with another person. Now you end up with a new dance partner. The same kind of thing can be compared to what occurs in a double replacement reaction in chemistry.

A double replacement reaction is a type of chemical reaction where two compounds react, and the positive metal ions and the negative nonmetal ions of the two reactants switch places, forming two new compounds or products.

Double replacement reactions take the form:

A⁺B^- + C⁺D^- → A⁺D^- + C⁺B^-

Prelab Questions:

1.    What happens in a Double Replacement Reaction?  Write in your own words.

2.    When you mix chemicals together, how do you know that a chemical reaction has occurred? (Evidence of a chemical reaction.)

Reaction #1:

Procedures:

1.    Goggles On!  No Lab Stools.  Do not sit on lab tables.

2.    Get a test tube of Sodium carbonate solution and a test tube of Calcium chloride solution.  Record their physical properties on the data table.

3.    Pour the two chemicals into a clean beaker.  Stir with a glass stir stick or plastic spoon.

4.    Record what happens on your data table.  What proof of a chemical reaction do you see?

5.    Clean up:  Return test tubes to Mrs. Jenner.  Clean out beaker and clean stir stick or spoon.

6.    Answer questions

Data:

Physical Properties of Sodium carbonate
Physical Properties of Calcium chloride
Proof of a Chemical Reaction

Conclusion Questions:

1.    Optional:  Balance the chemical equation for this reaction.

Na₂CO₃    +   CaCl₂  ----------à     CaCO₃         +      NaCl

2.    Look at the two products of this reaction.  Sodium chloride is table salt.  Calcium carbonate is chalk.  What can you see forming in this reaction, table salt or chalk?  How do you know?  Use specific evidence from the lab.

3.    How is this reaction an example of a Double Replacement Reaction?  Be specific about reactants and products.

Reaction #2:

Procedures:

1.    Get a test tube of Copper sulfate and a beaker of Ammonia.  Record the physical properties of both. 

2.    Use a dropper to put drops of Ammonia into the Copper sulfate.  Record what happens with the first drops and what happens as you add more Ammonia.

3.    Clean up:  Return Ammonia beaker to the tray. DO NOT CLEAN.

                   Rinse out the Copper sulfate test tube very well.  Return to Mrs. Jenner.

Data:

Physical properties of Copper sulfate solution
Physical properties of Ammonia
Reaction adding small amount of Ammonia
Reaction adding lots of Ammonia

1.    Optional:  Balance the chemical equation for this reaction:

CuSO₄    +        NH₄OH     ------------à       Cu(OH)₂     +          (NH₄)₂SO₄

2.    What evidence do you have that a chemical reaction occurred?