AP Chemistry
Lab 0: Using the Principle That Each Substance Has Unique Properties to Purify a Mixture
Learning Objective 3.5: The student is able to design a plan in order to collect data on
the synthesis or decomposition of a compound to confirm the conservation of matter
and the law of definite proportions.
Learning Objective 3.3: The student is able to use stoichiometric calculations to
predict the results of performing a reaction that is assumed to go to completion in the
laboratory, and/or to analyze deviations from the expected results.
This experiment involves a major practice of chemists: separating substances in a mixture
by taking advantage of properties of the substances that are unique to each one. In this case, you
will rely on the substances’ chemical reactivity upon heating as the property that differs between
them. From antiquity, two very important substances in society have been obtained from a salt
mixture called natron. Natron has been harvested for thousands of years from dry lake beds. In
ancient Egypt, and still today, natron is blended with oil and used as soap. Natron primarily
consists of two substances, sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3).
Each of these substances, when separated, also has important uses. Sodium carbonate is used in
the manufacture of glass, as a water softener when doing laundry, as an additive in community
swimming pools to raise pH, and as an additive in foods. Sodium bicarbonate has many uses,
ranging from cooking and medical uses, to cleaning, pesticide, and fire extinguishing uses.
PreLab Questions: (Questions to get you thinking about how you’re going to solve
this problem.)
1. What is a substance? What is a mixture? How are they related?
2. What are some general characteristics of substances chemists use to separate mixtures
into individual substances?
3. What are some specific physical and chemical properties of both substances in your
mixture? Write down any pertinent chemical reactions you find.
4. Describe the process of heating to constant mass. Why might this be important for your
procedure?
Procedure/Goal:
You have a mixture of NaHCO3 and Na2CO3. How will you determine the relative amounts
(percentages) of NaHCO3 and Na2CO3 in a mixture of the two substances using stoichiometry?
Work in a group to devise a procedure to collect data for the aforementioned question. Below is a
AP Chemistry
Lab 0: Using the Principle That Each Substance Has Unique Properties to Purify a Mixture
list of materials available for you to use during your procedure.
**Be sure that your instructor has reviewed and approved your proposed procedure prior to
proceeding with your lab investigation.
Other questions to consider when planning your procedure:
What mass of the mixture will you start with?
How many trials will you run?
Materials
•mixture of NaHCO3 and Na2CO3
•Balance, 0.001g
•Ring stand
•Crucible and lid
•Iron ring
•Crucible tong
•Ceramic triangle
•Bunsen burner
Safety
Do not heat covered crucibles. Always place the lid askew on top of the crucible while heating.
Wear goggles. Do not touch hot crucibles. **Review how to properly handle a crucible using
crucible tongs**
Data Collection and Calculations
Record your data and observations as you carry out your experiment in an organized manner of
your own design.
Data Analysis and Conclusion:
See Handout on AP Lab Report format—on my Como Park Website, Unit 0 Resources