Chemical Quantities - How Much is that Oxygen
in the Window?
Section IA – Vocabulary
Below is a list of all of the vocabulary terms used in this subunit. By the end of the
subunit, you will be able to write a working definition of each term and correctly
use each term.
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Avogardro's number
empirical formula
gram atomic mass
gram formula mass
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molar volume 
mole
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mol
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molar mass
percent composition
representative particle
standard temperature and pressure
STP
gram molecular mass
Section IB – Main Concepts
1) Moles and Matter
2) Mole-Mass and Mole-Volume Relationships
3) Percent Composition and Chemical Formula
Section 2 –– Outside Class Assignments
Thoughtfully do each of the following assignments. Include all your reasoning and
show all your work wherever it seems appropriate. Due dates for each assignment
will be given in class. (Please remember - homework that is passed in late is
automatically discounted 15%.)
1) Create a concept map for each of the following group of terms
a) Avogadro’s number, gram atomic mass, gram molecular mass, gram formula
mass, mole, and representative particle.
b) Molar volume, mol, molar mass STP and mole.
c) Per cent composition, chemical formula, molar mass, empirical formula.
2) Isaac Newton started off his legendary book Principia in 1686 with the first
ever definition of matter: “The quantity of matter is the measure of the same,
arising from its density and bulk conjointly.” (page 1).
a) What property of matter was he describing?
b) What is the density of matter?
c) What is the bulk of matter?
d) Restate his definition in your own words or use mathematical relationships if
that works better for you.
3) A mole is defined as 6.02 x 1023 representative particles.
a) What is a “representative particle”?
4)
5)
6)
7)
8)
9)
b) Is the representative particle for neon the same as for nitrogen? Explain
and give examples.
c) Why is the mole a useful measure when “doing” chemistry?
Examine Figure 7.7 on page 177 in your book.
a) What is a gam?
b) Why does sulfur “weigh” less than mercury but occupy a larger volume?
(Hint: think dense!!!)
c) Why do iron and carbon occupy about the same volume but have very
different masses? (Hint: think dense again!!!)
Compare a mole of table salt (NaCl) with a mole of sugar (C6H12O6)?
a) How is a mole of water similar to a mole of sugar?
b) Does a mole of table salt have a greater or smaller mass than a mole of
sugar? Show and explain your reasoning.
c) Which of the two compounds is denser?
i) Prove your answer mathematically. (Hint D = m/v)
ii) How would you prove your answer experimentally? (This is a trickster
question –can you get it?)
d) Does a mole of table salt occupy a greater or smaller volume than a mole of
sugar? Show and explain your reasoning.
Here are 3 quick variations on problems dealing with moles, representative
particles and gram atomic mass. Use this opportunity to practice setting up and
solving these three different types of problems. To receive credit you must
show step-by-step how you solved each problem and reached the correct
answer. (The same approach will be excepted on quizzes.)
a) What is the mass of 3.01 x 1011 atoms of sodium metal?
b) How many moles of sodium metal do 3.01 x 1011 atoms of sodium metal
comprise?
c) How many atoms are in 1.05 moles of sodium metal?
A glass jar holds 1 x 1023 molecules of water.
a) How many moles of water is this?
b) What is the mass of this amount of water?
c) How many grams of oxygen does this amount of water contain?
d) How many grams of hydrogen does this amount of water contain?
e) How many moles of oxygen does this amount of water contain?
f) How many moles of hydrogen does this amount of water contain?
g) Are the number of moles of hydrogen and oxygen the same or different?
Explain your answer.
See #1-8, 11-13, 15-16 in More Moles Worksheet for more practice problems.
Consider Figure 7.9 on page 179.
a) What is a gmm?
b) How is it different from a gam?
c) Of the three compounds in the figure, which contains the most molecules?
d) Of the three compounds in the figure, which contains the most atoms?
10) The common name for acetylsalicylic acid (C8H8O4) is aspirin.
a) What is the mass of 2 x 1011 molecules of aspirin?
b) How many moles of acetylsalicylic acid does this represent?
c) When acetylsalicylic acid is broken down, it releases all of its hydrogen and
oxygen as water. How many moles of water are released from the 2 x 1011
molecules of acetylsalicylic acid?
d) How many molecules of water are released?
e) What is the mass of the water that is released?
f) How many moles of carbon are left behind?
11) See # 1-3 and 5-8 in Atomic and Molecular Mass Worksheet for more practice
problems.
12) Sodium carbonate is one of two key ingredients in making thousand year old
eggs, a Chinese delicacy. The sodium carbonate breaks down the egg white into
simpler, tastier molecules such as ammonia, fatty acids and hydrogen sulfide.
a) What is the gfm of sodium carbonate?
b) One recipe calls for 100 grams of sodium carbonate. How many moles of
sodium carbonate does this represent?
c) How many grams of sodium are present in 100 grams of the compound?
13) Measuring the number of atoms and molecules in gases is a bit more tricky and
different considerations apply.
a) What does the abbreviation STP mean?
b) Do all substances exist as gases at STP?
c) The volume occupied by one mole of the solid phase of two different
compounds can be very different (Figure 7.7 p 177). (Remember your
element cube.) The volume occupied by their gaseous phases at STP is
defined as 22.4 liters. Explain why the volume is defined for a gas but not
for a liquid or a solid.
d) Why does a balloon containing 1 mole of hydrogen gas floats whereas the
same balloon containing 1 mole of neon sinks?
14) Element Project – Part III
a) What volume does 1M of your element occupy at STP?
b) Build a cardboard or paper box (and decorate it as you wish) that could hold
exactly 1M of your element at STP.
15) Which has the greater mass, 22.4 liters of water vapor at STP or 1 mole of ice
at 0oC? Show your argument and answer.
16) The density of a gas containing carbon and oxygen is 1.96g/L at STP.
a) Determine the molar mass of the compound.
b) Is the compound carbon monoxide or carbon dioxide? Show all your work and
your answer.
17) See # 9, 10, and 14 on More Moles Worksheet and #4 on Atomic and Molecular
Mass Worksheet for more practice problems with gases.
18) Examine Figure 7.13 on p 186 in your book.
a) Explain what this figure is trying to represent.
b) Does this figure help you understand the relationships among representative
particles, volumes and masses?
c) Would you build a different diagram to help you on a quiz or use this one?
d) If you have a better one, draw it on a separate index card. Otherwise copy
this one and annotate it if necessary. Be prepared to use this on a quiz in
class.
19) The mole is a critical concept used to help determine the composition and
empirical formulas of substances. The composition of a compound is determined
by reacting it with a variety of chemicals, and then identifying and massing the
resulting products. Set up and solve the following two percent composition
problems. Show all your work and the answer. Remember - No show, no credit.
a) A 9.03 g sample of Mg combines completely with 3.48 g of nitrogen to form a
compound.
i) What is the percent composition of Mg and N in the resulting compound?
ii) How many moles of Mg and N were present at the start of the reaction?
iii) How many moles of product were present when the reaction was
complete?
iv) What is the empirical formula of the product?
v) What is the molecular mass of the product?
vi) Was matter conserved? Explain and show your calculations.
b) A 14.2 g sample of mercuric oxide is decomposed into its elements by
heating. The result is 13.2 g of liquid mercury.
i) What is the percent composition of mercury and oxygen in the reactant?
ii) What is the empirical formula of mercuric oxide?
iii) How many moles of mercuric oxide are present at the start of the
reaction?
iv) How many moles of mercury are present at the end of the reaction?
v) Was matter conserved? Explain and show your calculations.
20) See the Percent Composition and Empirical Formula Worksheet for more
practice problems.
21) Every month the MWRA performs a water quality analysis. The table below
lists the results for May 2006. Quantities are recorded as micrograms (ug) or
milligrams (mg) in a liter of drinking water . Use this table to answer parts a, b,
and c of this question.
MWRA Water Supply Trace
Materials
Aluminum
<15.0
Ammonia
<0.01
Antimony
<1.0
Arsenic
<1.0
Barium 7.1
7.1
Beryllium
<0.3
Bromide
9.5
Cadmium
0.5
Calcium
2070
Chloride
7.8
Cyanide
<0.01
Fluoride
< 0.02
Iron
11.6
Lead
<1.2
Magnesium
504
Manganese
4.7
Mercury
0.01
Nickel
<5.0
Nitrate
0.005
Potassium
478
Silica (SiO2)
2180
Sodium
4.9
ug/l
mg/l
ug/l
ug/l
ug/l
ug/l
ug/l
ug/l
ug/l
mg/l
ug/l
ug/l
ug/l
ug/l
ug/l
ug/l
ug/l
ug/l
mg/l
ug/l
ug/l
mg/l
a) How many atoms of As are present in one liter of water?
b) How many moles of silicon dioxide (sand) are present in one liter of water?
c) Are there more moles of potassium or manganese per liter?
Section 3 –In Class Activities
1) Lecture / slides
2) Demonstrations
a) Calculating the moles in a name
b) Practice Problems
3) Student Labs and Activities
a) Counting by Measuring Mass
b) Measuring Mass as a Means of Counting
c) Percent Composition
4) Element Project –Part III
5) Practice Worksheets
a) More Moles Worksheet
b) Atomic and Molecular Mass Worksheet
c) Percent Composition and Empirical Formula Worksheet
Section 4 –Textbook and Further Readings
1) Wilbraham, Staley, Matta, Waterman, pp171-186; 188-189; 191-194