SCH3U
Name: ________________
Mass Relationships in a Chemical Reaction
Purpose
To determine the mass of Copper formed when Aluminum is reacts with a Copper salt.
Introduction
In this experiment, a piece of aluminum foil will .he placed in an aqueous solution of Copper II chloride. The reaction is
allowed lo go to completion. The mass of copper produced when a given mass of the copper compound reacts with a given
aluminum will be determined experimentally and compared to a theoretical yield calculated from an analysis (based on a
balanced equation) of which of the reactants is limiting and the expected mass of product.
Apparatus
2 150 mL beakers
graduated cylinder
stirring rod
tweezers
Materials
CuCl2•2H2O
Aluminum foil
watch glass
balance
hot plate
Procedure
Record all experimental results in the data table as soon as you obtain them.
a) Mass of first beaker (g)
b) Mass of beaker and dry Copper II chloride dihydrate
(g)
c) Mass of dry Copper II chloride dihydrate (g)
d) Mass of Aluminum foil (g)
e) Mass of beaker and Copper (g)
f) Mass of Copper (g)
g) Appearance of Copper II Chloride solution
h) Appearance of Aluminum
i) Appearance of the contents of the beaker after step C
j) Appearance of Copper after step H
A) Determine the mass of a clean, dry 150 mL beaker. To the beaker add approximately 2.5 g of
Copper II chloride dihydrate. Determine the mass of the beaker and contents. Add 50 mL of water.
Stir to dissolve the Copper compound.
B) Loosely fold a 6 cm x 5 cm piece of Aluminum foil lengthwise to make a 3 cm x 5 cm strip. Then
loosely fold this lengthwise again to make a 1.5 cm x 5 cm strip. Loosely coil the strip into a circle,
and place it in the solution so that it lies on its edge on the bottom of the beaker.
C) Place the beaker on a hot plate and heat the solution until it has boiled gently for 5 min. Avoid
overheating. There may be some Foaming during the early stages of the heating. Gently agitate the foil
to cause Copper to fall off and expose more Aluminum. Avoid removing any solid from the beaker
on the tweezers. Allow the solution to cool until you can hold it comfortably in your hands.
D) Carefully use tweezers to shake any remaining aluminum foil in the beaker to dislodge the Copper.
Remove the aluminum foil, being careful to leave the copper in the beaker. Rinse and dry this
Aluminum using filter paper and subtract its mass from the mass of Aluminum in the data table.
E) Pour the liquid in the beaker into the other beaker, being careful not to lose any copper. When you
are sure that no Copper has been lost, you may pour the contents of the second beaker into the sink.
F) Add 50 mL of water to the beaker. Stir gently to wash the copper and repeat step E. Repeat step F
G) Cover the beaker with a watch glass, and gently heat the beaker containing the wet copper to drive
off the water. When the initial spattering has stopped, remove the watch glass and continue the gentle
heating to drive off the last traces of moisture. Do not heat so strongly that the copper turns black.
H) Allow the beaker to cool, and determine the mass of the beaker and Copper.
Concluding Questions
1) Write a balanced chemical equation for this reaction.
2) Calculate the molar mass of
Aluminum: ____________ Copper:___________________
Copper II chloride dihydrate: ________________________________________________________
3) a) Determine the limiting reactant from the masses of the reactants and the balanced equation.
b) How does your answer to 3a compare to item “i” in the data table?
4) Calculate the theoretical yield of solid Copper.
5) Calculate the percent yield.
6) What was the purpose of heating the reactants in step C?
7) What was the purpose of Step F? What would be the consequences of omitting this step?