Facilitate the following procedures for students. Circulate around the laboratory to ensure safety of all students, as well as to make sure they are conducting the experiment without tremendous error.
Pre-Lab (homework from the night before)
- Ask students to consider the following unbalanced chemical reaction:
- aluminum + copper (II) chloride dihydrate àaluminum chloride + copper + water
- Aluminum metal reacts with aqueous copper (II) chloride dihydrate to form copper metal, aqueous aluminum chloride, and water. Write the correct balanced equation for this reaction.
- What does a solution look like when it contains dissolved copper (II) ions?
- For the balanced reaction, determine the mass of aluminum that would remain after a 10.00-g Al sample and 1.00 g of CuCl2·2H2O fully reacted. Show your work fully.
- Tell students that they must answer the following question: What are the limiting and excess reactants of our lab experiment?
- Students should compare pre-lab homework answers with their lab group. Discuss among group members if there are discrepancies.
- Gather all the materials needed for the lab, and begin your experiments!
Note: Usual lab groups should have picked out a number from a hat during the previous day. The number indicates the amount of aluminum and copper (II) chloride dihydrate (in grams) they will be working with in the lab.
Using the chart below, select your group number and the mass of aluminum metal and copper (II) chloride dihydrate that you will be using in this activity.
Mass of Al (g)
Mass of CuCl2·2H2O (g)
- Weigh out the copper (II) chloride dihydrate in a 250 mL beaker.
- Using a graduated cylinder, measure out exactly 100 mL of water (tap water is fine) and add it to the beaker containing the copper (II) chloride dihydrate. Stir until the salt dissolves completely. Note the color of the solution in your lab notebook.
- Weigh out the appropriate mass of aluminum foil, crumple up into a few small pieces and add it to the copper (II) chloride dihydrate solution. Stir the solution gently and then allow it to sit undisturbed for 5 – 10 minutes. Write observations in your lab notebook.
- At the end of the period, label your beaker and cover it with a watch glass. Your teacher will designate an area to store your beakers overnight. In the following class time, you will be able to confirm the identity of the limiting reactant.
- See Limits and Excess Lesson PPT for suggestions on how to present the lesson and manage class time.
- Please be aware that this lab is not an original lab. It is commonly used in AP Chemistry classes as well as Honors Chemistry classes.
- Wear safety goggles during this experiment. Avoid skin contact with copper (II) chloride dihydrate. Wash your hands before leaving the laboratory.
- Check all the students before starting the experiment.