LAB: DECOMPOSITION OF COPPER (II) CARBONATE
Purpose: To prepare and test for carbon dioxide by decomposing CuCO3
Procedure:
I. Perform a common laboratory test for carbon dioxide. Pour 5 mL of limewater (a solution of
calcium hydroxide) into a small test tube. Using a straw, gently blow your breath into the limewater
for about 30 seconds. Record your observations on your lab report.
II. Preparation of carbon dioxide by decomposition of a carbonate.
1. Weigh and record the mass of a large test tube that is clean and dry.
2. Weigh out about 2 grams of copper (II) carbonate into the large test tube. Record the exact
weight of the test tube + copper (II) carbonate on your lab report.
3. Insert a rubber stopper fitted with a rubber delivery tube into the
mouth of the large test tube. (See diagram.) Clamp the test tube to
a ring stand. Insert a glass tube into the end of the rubber delivery
tube. Pour 5 mL of limewater into a small clean test tube.
Heat the test tube containing the CuCO3 until you see a change in
color. Then insert the glass tube into the limewater. Observe the
appearance of the limewater as gas given off by the reaction forms
bubbles in the limewater. Continue heating until all of the CuCO3 has
changed color. Remove the delivery tube from the limewater when
the reaction is complete. Record your observations on your lab
report. Be sure to describe the appearance of both of the solids and the gas formed.
4. The solid chemical left in the test tube after the reaction is called the residue. After the test tube
containing the residue has cooled, weigh it and record the mass of the test tube + residue on your
lab report.
Analysis: Answer the following questions on your lab report.
1. State the evidence that heating the CuCO3 resulted in a chemical change.
2a. What is the identity (name) of the gas?
2b. What evidence do you have for your answer to 2a?
3. Calculate the mass of the CuCO3 you weighed out. Show your work.
4. Calculate the mass of the residue. Show your work.
5. How can you explain the difference in mass?
6. The residue in this reaction is copper (II) oxide. Write a balanced equation for the reaction.
(Write the symbol for heat over the arrow and indicate the state of matter of reactant and products.)
Under your equation, write a sentence that describes the reaction.