PRACTICE TEST for HONORS CHEMISTRY EXAM 2: ATOMS
1. Prepare a summary of Chapter 4 in your text, in the format of your choice (outline, concept map . . .).
a
b
c
d
e
2. Describe what each box represents (e.g., drawing (a) represents a pure monatomic element)
3. Draw circle pictures to illustrate each of these.
a. 4 molecules of A2
c. 2 molecules of A2 and 2 molecules of B2
b. 4 molecules of A2B
d. 2 molecules of A2B and 2 molecules of AB
4. Fill in the blanks to complete these paragraphs. In your response, write the entire paragraph, not just
the missing words.
The Greek philosopher _____ was among the first to suggest the existence of atoms, but the modern
idea of the atom began with ______’s atomic theory in the year 1808. A few years later, in ____,
Amadeo Avogadro stated his hypothesis that _____________ to explain why gases combine in
simple, whole number ratios. His hypothesis later became the basis for the mole, the counting unit of
chemistry. One mole contains _____ particles.
Almost a century later, in _____, the English physicist __________ discovered the electron and
showed that the atom was made of even smaller particles. He thought the atom was like a blueberry
muffin, but in the year ____, __________ did an experiment in which he directed alpha particles at a
thin sheet of gold foil. He expected that _______________, but to his astonishment ____________!
From this experiment, he proposed the nuclear model of the atom, in which _______________.
5. a. List the 3 subatomic particles we studied, including their charge and mass in amu.
b. Describe the arrangement of these particles in the atom.
c. Compare the size of the nucleus to the size of the atom [hint: it involves football]
6. What are isotopes? How will the symbols of isotopes be alike? how will they differ?
7. Fill in this table:
Symbol Protons Neutrons Electrons Atomic number Mass number
131
I
47
61
38
90
9
19
8. Rubidium is 72.17% 85Rb (84.9117 amu) and 27.83% 87Rb (86.9178 amu). Calculate the average
atomic mass of Rb. Don’t forget units and watch your sigfigs.
9. Get a blank periodic table and label it with this information:
• period numbers
• alkali metals
• group number, old and new
• alkaline earths
• the staircase
• halogens
• metal, non-metal, and semi-metal regions
• noble gases
• transition metals
• group and period trends in atomic size
10. Is hydrogen a metal or a nonmetal? To which family does hydrogen belong?
Review
11. Do these mole conversions. Setups with units required; round answers to the appropriate number of
sigfigs.
a. What is the mass of 1.63 mol He?
b. How many moles are in 68 grams of Co?
c. What is the mass of 0.0058 mol NaOH?
d. How many moles are in 25.84 g CO2?
e. How many atoms are in 0.560 moles of Pb?
f. How many molecules are in 3.75 mol NH3?
12. Repeat three times: my chemistry teacher is obsessed with units. I will put units on every step of
every calculation on the exam.
13. What is the percent yield when 5.22g of O2 reacts with H2 to produce 3.00 grams of water.
2H2 + O2  2H2O
ANSWERS to PRACTICE TEST for EXAM 2
a
b
c
d
2. a. pure monatomic element
b. pure compound
d. mixture of two different elements & one compound
e
c. pure diatomic element
e. pure compound
3.
a. 4 molecules of A2
b. 4 molecules of A2B
c. 2 molecules of A2
and 2 molecules of B2
d. 2 molecules of A2B
and 2 molecules of AB
4. The Greek philosopher Democritus was among the first to suggest the existence of atoms, but the
modern idea of the atom began with John Dalton’s atomic theory in the year 1808. A few years later,
in 1811, Amadeo Avogadro stated his hypothesis that equal volumes of two gases at the same
temperature and pressure contain equal numbers of molecules to explain why gases combine in
simple, whole number ratios. His hypothesis later became the basis for the mole, the counting unit of
chemistry. One mole contains 6.02 x 1023 particles.
Almost a century later, in 1897, the English physicist J.J. Thompson discovered the electron and
showed that the atom was made of even smaller particles. He thought the atom was like a blueberry
muffin, but in the year 1911, Ernest Rutherford did an experiment in which he directed alpha
particles at a thin sheet of gold foil. He expected that all the particles would go through the foil, but
to his astonishment some were bounced back! From this experiment, he proposed the nuclear model
of the atom, in which all the positive charge and almost all the mass are concentrated in a tiny
nucleus, with electrons distributed around the nucleus.
5. a. See Table 4.1 on pg 106. Proton mass ≈ neutron mass = 1 amu; electron mass = 0.00054 amu.
b. Protons & neutrons in tiny nucleus; electrons occupy rest of atom’s volume around nucleus
c. If atom = football stadium, nucleus = marble on 50-yard line
6. Isotopes are atoms with the same number of protons but different numbers of neutrons. They have the
same chemical symbol and the same atomic number (lower left corner of symbol), but different mass
numbers (upper left corner). For example, 36 Li and 37 Li are isotopes of lithium.
7.
Symbol Protons Neutrons Electrons Atomic number Mass number
131
I
53
78
53
53
131
108
Ag
47
61
47
47
108
90
Sr
38
52
38
38
90
19
F
9
10
9
9
19
8. (0.7217)(84.9117 amu) + (0.2783)(86.9178 amu) = 85.47 amu. Watch your sigfigs.
9 & 10. Check the back cover of your textbook. H is a nonmetal that does not belong to any family.
11. Setups with units (including setups for molar mass where needed) are required; watch your sigfigs.
a. 6.52 g b. 1.2 mol c. 0.00015 mol d. 0.5871 mol e. 3.37 x 1023 atoms
f. 2.26 x 1024 molecules
12. Don’t say I didn’t warn you!
13. What is the percent yield when 5.22g of O2 reacts with H2 to produce 3.00 grams of water.
2H2 + O2  2H2O
1)
5.22 g
x 1 mole O2
32.00 g
2)
0.1631 mole O2 x 2 moles H2O =
1 mole O2
0.32625 moles H2O
3)
0.32625 moles H2O x
5.8725 grams H2O
theoretical yield
Percent Yield = Actual yield
Calculated yield
3.00 grams H2O
5.88 grams H2O
=
18 g
=
1 mole H2O
0.163125 mole O2
x 100
x
100 =
51.1 %