Where oh where did my aluminum can go?
CAUTION: The chemicals used in this experiment are very strong acids and bases. They are stronger than
anything you have ever worked with. Please take all appropriate safety precautions.
I can design an experiment to capture a gas and identify it.
I can use safe and proper lab techniques when working w/ strong acids & a variety of materials.
Prepare the can:
Clean and dry an aluminum pop can. You must also sand off the paint and coating inside and out. For
the experiment you need about 1 gram of aluminum. Be sure to note the exact mass. What might you
do to the aluminum to get it to react quickly (as opposed to taking all day to react)?
Design the experiment:
A gas will be produced in this chemical reaction. You will need to measure the rate of gas production
and the total volume of gas produced. You want to design this experiment before you get started. You
also need to establish the identity of the gas by verifying three physical and one chemical properties.
You will also need to keep track of the temperature of the reaction over time.
Start the experiment:
1) Place the aluminum in a 250 ml Erlenmeyer flask and carefully add 50 ml of 4 M potassium
hydroxide. Allow the reaction to go all the way to completion. Attempt to write a balanced chemical
equation for this reaction (Hint: there is a tetrahydroxyaluminate ion formed as part of the reaction).
2) Carefully filter the reaction mixture and collect the filtrate in a 250-ml beaker. Discard the filtered
residue.
3) Carefully and slowly add 30 ml of 9 M sulfuric acid to the filtrate while stirring. It gets really HOT
so go slowly! Leave the solution sit in the beaker until the next class. Attempt to write a balanced
chemical equation for this reaction.
4) By the next class you should have a product formed. If so, cool the product in an ice bath. Then
filter the product and wash with a little bit of very cold water. Leave the product to dry. Leave the
original filtrate sit one more lab period to see if more product forms and repeat the filtration to collect
any more product.
5) If your teacher asks you to, recrystalize the product in 100 ml of hot water. Then let cool and sit
overnight. Cool and filter as above.
6) Collect all the dried product in one container and mass the product. Label it and save for a future
lab. What is the final product? How might you verify what you think the final product is?
Analysis:
1) What is the rate of gas production (report the rate)?
2) How much total gas was produced?
3) What is the gas and how do you know? (state the 3 physical and 1 chemical properties you tested).
4) Graph the rate of gas production. Use real graph paper!
5) Graph the temperature change during the reaction.
6) Do you think the final product is a pure substance? Why or why not?
7) What can you conclude about the reaction rate based on your experiment? What variables affect the
rate?
8) Where exactly did the aluminum can go?