HONORS CHEMISTRY: Separation of a Mixture Lab (Nelson, Kemp, et. al.)
Background: This activity requires you to separate a mixture of sodium chloride, ammonium chloride, and
silicon dioxide (sand). Of course, the separation will need to be complete and you are required to provide the
mass in grams of each component of the mixture. For more information that may help you in your quest to
separate this mixture, please refer to the class notes, the textbook, and the internet for the properties of each
of the compounds.
Some additional info:
1. You will be given the mixture in an evaporating dish. The teacher will prepare a list of accepted values for
each component as each mixture is prepared.
2. NH4Cl behaves like NaCl, in all ways. Additionally, NH4Cl can also behave like dry ice when heated
gently.
3. You may use any other equipment that will allow you to successfully complete the lab, however, certain
pieces will be required.
4. One lab will be handed in by each group. It must be typed and emailed to me at ____________________
by ______________________________________. Points will be deducted for group work and safety issues.
Pre Lab Questions (a copy of Table 2.1 can be found on the lab tables)
1. Classify each of the following as a pure substance or a mixture; if it is a mixture, state whether it is
heterogeneous or homogeneous: (a) concrete, (b) tomato paste, (c) sea water, (d) iron.
2. Suggest a way to determine whether a colorless liquid is pure water or a salt solution without tasting
it.
3. What distinguishes a mixture from an impure substance?
4. Define the process of sublimation.
5. How do decantation and filtration differ? Which should be faster?
6. Why should you never place a hot object directly on the pan of a balance?
7. How does this experiment illustrate the principle of conservation of matter?
8. A mixture was found to contain 1.05 g of SiO2, 0.69 g of cellulose and 1.82 g of calcium carbonate.
What percentage of calcium carbonate is in the mixture?
9. How could you separate a mixture of acetone and α–naphthol? Refer to Table 2.1 for physical
properties.
10. How could you separate zinc chloride from SiO2?
11. A student found that her mixture was 13% NH4Cl, 18% NaCl and 75% SiO2. Assuming that her
calculations are correct, what did she most likely do incorrectly in her experiment?
12. Why would it be beneficial to extract NaCl with water from the mixture three times as opposed to
only once?
General Directions:
Step 1: Observe and State the Problem (Purpose of the lab)
-From the information in the Background and additional info sections, you are aware of the problem that
needs solving. In one brief statement please summarize this problem (state the purpose of this lab).
Step 2: Form a Hypothesis
-A hypothesis is a statement that reflects what the researcher predicts will happen as a result of her or his
experiment. This statement (or set of statements) is grounded in research that relates to the topic being
studied. It is not simply a guess. Use your notes, answers to the pre lab questions and other information to
hypothesize how you believe the mixture will be best separated (the order and method that each
compound must be use to separate the compound from the mixture). For example, "Compound ___ must be
removed first by adding _____..." etc.
Step 3: Design an Experimental Procedure
-Write, step by step, your plan for separating the mixture. Don’t leave out the small details! Complete your
pre lab questions in a thoughtful manner.
-Create data tables for use during lab
-The procedure you write must be approved by your teacher before you begin experimentation.
Step 4: Collect and Analyze Data
-Following your procedure, you will carry out an experiment that attempts to separate your mixture.
-The goal is to end up with three separate masses, one for each of the three components of the mixture.
Record all data in appropriately constructed data tables.
-Perform the appropriate calculations (masses of each substance, percent recovery and percent error). Show
all work.
- Prepare 2 graphs:
a. Graph of the comparison of the experimental masses (your values) to the actual masses
(the real masses of each compound). Use the correct type of graph and include these items: title,
labels for axes, a key itemizing what each color/symbol represents and the proper numeric scale on
the y axis.
b. Create a graph showing the percent composition of the mixture. Use the correct type of
graph and include these items: title and labels for the parts composing the mixture.
Step 5: Conclude
-Your conclusion will explain whether or not you were successful in supporting your hypothesis. If you were
successful, explain why! If you were not, explain why! If you were not successful, IT DOES NOT MEAN
THAT YOUR EXPERIMENT WAS A FAILURE!
Post Lab Question
1. Could you have separated the components of your mixture in a different order than what you did in
lab? Explain.