Take Home Lab #9: The Mole
Question: What does a mole of different substances look like?
Safety: Baking soda can harm your eyes. Dispose of all chemicals,
clean up all spills, and wash your hands when finished.
Materials: Balance, pre-1982 pennies, water and baking soda.
Procedure: Because atoms and molecules are so small, chemists created
a quantity called a mole that represents a large number of atoms. The unit of a
mole is like a dozen in that it represents a certain number of atoms or
molecules. It is a very, very, very large number but the same idea as a pair, a
dozen, a gross, and so on. A pair is 2 items, a dozen is 12 items, a gross is
144 items, and a mole is 6.0 x 1023 items (molecules or atoms). That
is 600,000,000,000,000,000,000,000 items in a mole. But what does a mole of a
substance look like? You will find out in this activity.
In
this activity, you will use your balance to measure out approximately 1 mole of
different substances. Recall from the experiment where you built your balance
that the density of water is 1.0 g/mL. Therefore, 1 mL of water has a mass of 1
g. You will use this information and the periodic table to determine how much
of each substance composes a mole.
The
periodic table tells you the mass of a mole of each element. For example, the
mass of a mole of carbon is 12.011 g. To find the mass of a compound, you
simply add up the masses of each element that makes up the compound. For
example, a mole of calcium carbonate (CaCO3) would have a mass of
approximately 100 g (40.078 + 12.011 + 3[15.999] = 100.086g). Your balance is
not sensitive enough to measure the 0.086 grams, so for take-home labs we will
just ignore that part and round it to 100 g.
Use
your balance, the periodic table, and the known density of water to determine 1
mole of the following items. Describe how much of each makes up 1 mole (for
example; seven and a half pennies, a large handful of sand). If a mole of the
substance is very large, you may measure half a mole or one-tenth of a mole and
then describe what a full mole would look like.
Data:
|
Substance
|
Number of grams
|
Description
|
|
Pennies (pre-1982 pennies are pure
copper and post-1982 pennies are not, so use pre-1982 pennies)
|
|
|
|
Water (H2O)
|
|
|
|
Sand (Pure sand is SiO2;
assume that your sand is pure.)
|
|
|
|
Baking soda (sodium bicarbonate, NaHCO3)
|
|
|
Post-Lab Questions:
1. How many 500 mg aspirin tablets
would it take to make a mole of aspirin? (C9H8O4)?
2. Which would be heavier, a mole of
sodium chloride or a mole of potassium chloride? Explain.
3. Why can you not determine the mass
of a mole of most mixtures?
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