Quantitative Analysis: A Single Displacement Reaction
Dr. Slotsky Chemistry I
Reaction: 2 Al + 3 CuSO4  Al2(SO4)3 + 3 Cu (NaCl catalyst)
Procedure:
Measure out 70 mL of 0.5 M CuSO4 solution into your beaker.
Weigh out 0.5 grams of aluminum foil, get as closely as you can. Because
the scales are not perfectly zeroed, you may wish to use a weighing boat and add
0.5 g to the mass of the boat and add until rebalanced.
Add the aluminum foil to the CuSO4 solution and stir with wooden stick.
1)
Do you observe signs of a chemical reaction? Watch for 1 or 2 minutes.
Sometimes reactions require a catalyst to proceed at a useful speed. The
catalyst for this reaction is ordinary table salt (NaCl). Weigh out 1 gram of NaCl
and stir it into the reaction.
2)
Do you observe signs of a chemical reaction? Watch until reaction appears
complete.
At this point, the aluminum should have entirely dissolved and orange
copper metal should be visible in your solution. Collect it on filter paper, squeeze
out water and allow it to dry. Measure the mass of your copper metal using a
weighing boat:
3) Boat empty: _____g
With Cu metal: ______ g
Net mass of Cu ______g.
Continued on back
Reaction: 2 Al + 3 CuSO4  Al2(SO4)3 + 3 Cu (NaCl catalyst)
Analysis:
Notice the coefficients in the above reaction: these are in MOLES. In this
reaction, 2 MOLES of aluminum will displace 3 MOLES of copper metal from
solution. Let’s check to see if we observe this same mole ratio that we expect
from the balanced equation:
4)
Calculate the number of moles of Al and Cu in this reaction.
0.5 grams of Al = _____________________ moles of Al (divide by mass of Al)
__________ grams of Cu = ____________ moles of Cu (divide by mass of Cu)
5)
Calculate the molar ratio of Cu and Al.
______ moles Cu ÷ ________ moles Al = ___________________
We would expect this, from the balanced equation, to be 1.5 (3 ÷ 2).
Is this close to what we observe? Why do you think your result may differ
from theory?