Decomposition of Malachite
Do not write on this copy. Leave this copy in the classroom at the close of period.
Your paper should include Title, Purpose, Data Table (see reverse side),
Calculations with set-ups, and a summary.
Introduction: Malachite is a complex chemical having a formula of
CuCO3•Cu(OH)2•XH2O. Notice that the exact amount of water in the formula is a
variable. In this case the production of products cannot be known precisely by
calculations. What we intend to do is to predict the amount of CuO produced by
malachite as if it were anhydrous CuCO3•Cu(OH)2. The amount of CuO will be less than
expected because the starting formula is really CuCO3•Cu(OH)2•XH2O, and we do not
know the amount of hydrated water (X). Since we expect less CuO than the calculated
amount we will determine the percent yield. The percent yield will be the theoretical yield
based upon the equation listed below.
CuCO3•Cu(OH)2 ---> 2 CuO + CO2 + H2O
Purpose: In this experiment, you will measure between 0.100 to 0.200 grams of
malachite into an evaporation dish, determine the mass of CuO produced and determine
the percent yield.
Procedure:
1. Check the evaporating dish for dryness. You may need to dry it thoroughly before
proceeding.
2. Set the balance to zero. Next place the evaporating dish with a stirring rod resting on
the dish onto the balance pan. Record the mass of both the dish and rod.
3. Add between 0.100 to 0.200 grams of malachite into an evaporation dish. You may
need to set the stirring rod aside for a moment while adding malachite, but be sure you
measure and record the mass of the dish + rod + malachite.
4. Place the dish on a hot plate and heat it. Use the stirring rod occasionally for stirring
the powder. The powder will start green to become brown and finally black. When it is
all black (no brown specks left) stop heating.
Do not allow the rod to set on the dish or hot plate or it will burn you when you pick
it up to occasionally stir.
6. While heating the dish, carry out problem one under calculations.
7. Remove the dish from the hot plate with crucible tongs and place the dish onto a wire
mesh to cool.
8. After the dish is cool enough to handle, determine the mass of the dish + rod + CuO.
Table:
Dish + Rod + malachite
Empty Dish + Rod
Dish + Rod + CuO
________________g
________________g
________________g
Calculations:
1. Using your measured amount of malachite, CuCO3•Cu(OH)2,
determine the grams of CuO expected.
CuCO3•Cu(OH)2 ---> 2 CuO + CO2 + H2O
2. What is meant by theoretical yield?
3. What was the actual yield?
4. Determine the percent yield.
Theoretical
%yield 
x100
actual
5. Based upon the amount of CuO produced, how many grams of H2O CO2 were also
produced?
6. Based upon the amount of CuO produced, how many grams of CO2 were also
produced?
7. At STP how many liters of CO2 are produced?
8. Assume the pressure is 735 mmHg and the room temperature is 25°C, what is the
volume of CO2 produced?
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