Chemistry 1A Fall 2009
Exam 1 Key Chapters 1-3
Electronegativities
H
2.2
Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Na
0.93
Mg
1.31
Al
1.61
Si
1.9
P
2.19
S
2.58
Cl
3.16
K
0.82
Ca
1.0
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Rb
0.82
Sr
0.95
In
1.78
Sn
1.96
Sb
2.05
Te
2.1
I
2.66
Cs
0.79
Ba
0.89
Tl
2.33
Pb
2.02
Bi
2.0
Po
2.2
Substance
battery acid
benzene, C6H6
blood (whole)
bromine, Br2
chocolate
copper, Cu
chromium(III) oxide, Cr2O3
gasoline
gold, Au
iron, Fe
magnesium, Mg
nitrobenzene, C6H5NO2
oleic acid
phosphorus oxychloride, POCl3
sulfuric acid (concentrated)
water at 20 °C
Density in g/mL
1.29
0.879
1.05
3.12
1.75
8.94
5.2
0.7025
19.0
7.87
1.74
1.20
0.895
1.675
1.84
0.997
1
Xe
2.6
Answer the following by writing the word, words, letter, letters or number in each blank
that best completes each sentence. (2 points each unless stated otherwise)
1.
The evaporation of ethyl alcohol is a physical (chemical or physical) change.
2. A(n) heterogeneous mixture is a mixture with two or more phases.
3. Metalloids or semimetals are the elements that have some but not all of the
characteristics of metals.
4. A substance that is malleable is capable of being extended or shaped by the blows of a
hammer.
5. The symbol for the element gold is Au, for cadmium is Cd, and for tin is Sn. (1 point each)
6. The name of the element with the symbol Pt is platinum, F is fluorine, and Mn is
manganese. (1 point each)
7. The name of the group on the periodic table to which strontium belongs is alkaline earth
metals.
8. The element iron is in the 4th period on the periodic table.
9. The accepted SI unit for energy is the joule and its abbreviation is J.
10. The metric prefix nano means 10−9, and its abbreviation is n.
11. A(n) cation is an ion formed from an atom that has lost one or more electrons and
thus has become positively charged.
12. Precision describes the closeness in value of a series of measurements of the same
entity. The closer the values of the measurements, the more precise they are. Accuracy
describes how closely a measured value approaches the true value of a property.
13. A(n) empirical formula is a chemical formula that includes positive integers that
describe the simplest ratio of the atoms of each element in a compound.
14. Isomers are compounds that have the same molecular formula but different molecular
structures.
15. Alcohols are compounds that contain a hydrocarbon group with one or more -OH
groups attached.
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16. Draw a reasonable Lewis structure for CH3COF. (4 points)
17. Write the name of the substance below. (3 points)
2,2,4-trimethylpentane
18. Identify each of the following as a binary covalent compound, a binary ionic compound, a
binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar.
Write name for each. (9 points)
Chemical Formula
Type of Substance
Name
Sr(H2PO3)2
ionic with polyatomic ion
strontium dihydrogen phosphite
HF(aq)
binary acid
hydrofluoric acid
C2H5OH
alcohol
ethanol
Ni(C2H3O2)3
ionic with polyatomic ion
nickel(II) acetate
H2SO3
oxyacid
sulfurous acid
SO2
binary covalent
sulfur dioxide
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19. Identify each of the following as a binary covalent compound, a binary ionic compound, a
binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar.
Write formula for each.) (9 points)
Chemical Formula
Type of Substance
Formula
hydrobromic acid
binary acid
HBr(aq)
chromium(III) sulfide
binary ionic
Cr2S3
calcium bicarbonate
ionic with polyatomic ion
Ca(HCO3)2
perchloric acid
oxyacid
HClO4
glucose
sugar
C6H12O6
aluminum hypochlorite
ionic with polyatomic ion
KClO4
20. Complete the following table by (1) writing the name for the type of particle viewed as
forming the basic structure of each of the following substances and (2) writing the name of
the type of attraction the is broken when these substances are melted or boiled, e.g. covalent
bonds, dipole-dipole attractions, etc. (14 points)
Substance
Particles to Visualize
Type of Attraction
carbon in the diamond
form
atoms
covalent bonds
CH3NH2
molecules
hydrogen bonds and London
forces
scandium sulfite
Sc3+ cations and SO32− anions
ionic bonds
phosphorus
molecules
London forces
zinc
cations in a sea of electrons
metallic bonds
hydrogen chloride
molecules
dipole-dipole attractions and
London forces
methylbutane
molecules
London forces
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For the following numerical problems, be sure to carefully show your work and round your answer using the appropriate guidelines.
NOTE: Remember that there is part credit for each problem. Even if you cannot do all of a problem, be sure to set up as much of it as
you can. (8 points each)
21. You fill your tank with gasoline that is 4.2% by mass hexane, C6H14. If the tank contains 2.44 lb hexane, what volume in gallons of gasoline
did you add?
⎛ 453.6 g ⎞ ⎛ 100 g gas. ⎞ ⎛ 1 mL gas. ⎞ ⎛ 1 L ⎞ ⎛ 1 gal ⎞
? gal gas. = 2.44 lb hex. ⎜
⎟⎜
⎟⎜ 3
⎟⎜
⎟⎜
⎟ = 9.9 gal gas.
⎝ 1 lb ⎠ ⎝ 4.2 g hex. ⎠ ⎝ 0.7025 g gas. ⎠ ⎝ 10 mL ⎠ ⎝ 3.785 L ⎠
22. Chromium metal is used in metal alloys and as a surface plating on other metals to minimize corrosion. It can be obtained by
reducing the chromium(III) in chromium(III) oxide, Cr2O3, to the uncharged metal with finely divided aluminum. What mass of
Cr2O3, in megagrams, must be used to make 897 kg chromium, Cr?
⎛ 103 g ⎞⎛ 1 mol Cr ⎞ ⎛ 1 mol Cr2O3 ⎞ ⎛ 151.990 g Cr2O3 ⎞ ⎛ 1 Mg ⎞
? Mg Cr2O3 = 897 kg Cr ⎜
⎟⎜
⎟⎜
⎟ ⎜ 6 ⎟ = 1.31 Mg Cr2O3
⎟⎜
⎝ 1 kg ⎠⎝ 51.9961 g Cr ⎠ ⎝ 2 mol Cr ⎠ ⎝ 1 mol Cr2 O3 ⎠ ⎝ 10 g ⎠
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Answer the following in short answer form.
23. Write an explanation for why electrons affect the chemical characteristics of an atom,
write an explanation for why protons affect the chemical characteristics of an atom, and
write an explanation for why neutrons do not affect the chemical characteristics of an
atom. (6 points)
Electrons can be lost, gained and shared, so they are actively involved in chemical changes.
Their negative charge is felt by surrounding atoms, also affecting chemical changes.
Although protons remain in the nucleus of atoms in chemical changes, their positive
charge is felt by surrounding atoms. The number of protons also determines the number of
electrons in uncharged atoms.
Neutrons stay in the nucleus and have no charge.
24. Write a description of the element bromine as it is found at room temperature and
pressure. Your description should include mention of the particles that form its structure,
whether it’s a gas, liquid, or solid, how the particles are moving, how much space they
occupy, and the strengths of attractions between the particles. (8 points)
Bromine is composed of diatomic molecules, Br2, with 35 protons and a +35 charge in each
of the two nuclei surrounded by a −70 electron-charge cloud.
Bromine is a liquid at room temperature and pressure so the particles occupy about 70% of
the volume of the liquid. Attractions are strong but not strong enough to keep particles from
moving throughout the liquid. Constant collisions lead to changes in direction and velocity.
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