Chem is try
Chemistry Midterm Review Solutions
1.
Write each of the following in scientific notation:
a. 55 000 m
5.5 x 104
b. 480 g
4.8 x 102
c. 0.000 005 cm
5 x 10-6
d. 0.000 14 s
1.4 x 10-4
2.
In each of the following pairs, which number is larger?
a. 7.2 x 103 cm or 8.2 x 102 cm
b. 4.5 x 10-4 kg or 3.2 x 10-2 kg
3.
Write the following as standard numbers:
a. 8.25 x 10-2 kg
0.0825 kg
b. 8.75 x 104 cm
87,500 cm
4.
How many significant figures are in each of the following measured quantities?
a. 11.005 kg
5
b. 0.000 32 m3
2
c. 4.00 m
3
5.
Write the following in scientific notation with two significant figures:
a. 5000 L
5.0 x 103
b. 30 000 g
3.0 x 10-4
c. 0.000 25 cm
2.5 x 10-4
d. 0.000820 kg
8.20 x 10-4
6.
Perform the calculation and round to the correct number of significant figures:
a. 45.7 x 0.034
1.6
b. (0.2465 x 25) / 1.78
3.5
7.
Perform the calculation and round to the correct number of decimal places:
a. 45.48 cm + 8.057 cm
53.54 cm
b. 23.45 g + 1.041 g + 0.025 g
24.52 g
c. 1.08 L - 0.585 L
0.50 L
8.
Complete each of the following equalities:
a. 1 m = __100__ cm
b. 1 nm = _1 x 10-9_ m
c. 1 mm = __1 x 10-3__ m
d. 1 L = ___1 x 103___ mL
e. 1 g = ___1 x 10-3___kg
f. 1 g = __1 x 103___ mg
9.
1 g = 1 x 10-3 kg
1 g = 1 x 102 cg
1 g = 1 x 103 mg
1 g = 1 x 106 µg
1 g = 1 x 109 ng
For each of the following pairs, which is the larger unit?
a. milligram or kilogram
b. cm or um
c.
d.
mg or g
cm or mm
10. Use metric conversion factors to solve the following:
a. The height of a student is 175 cm. How tall is the student in meters?
175
b.
1m
= 1.75 m
1x102 cm
A cooler has a volume of 5500 mL. What is the capacity of the cooler in L?
1L
5500
= 5.5 L
1x103 mL
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c.
A hummingbird has a mass of 0.0055 kg. What is the mass of the hummingbird in g?
0.0055
d.
1g
= 5.5 g
1x10-3 kg
The daily requirement of phosphorus is 800 mg. How many grams is this?
1g
800
= 0.8 g
1x103 mg
11. Determine the density:
a. A 20.0 mL sample of a salt solution has a mass of 24.0 g
density =
mass
volume
24.0
= 1.20 g/mL
20.0
b.
A gem has a mass of 4.50 g. When the gem is placed in a graduated cylinder
containing 2.00 mL of water, the water level rises to 3.45 mL
3.45 – 2.00 = 1.45 mL (volume of the object)
4.50 = 3.10 g/mL
1.45
12. Explain the difference between accuracy and precision.
Accuracy is based on proximity to the true value,
while precision is based on the proximity of a set of numbers to one another
3 Matter

Physical and chemical properties and changes; Pure substances: elements and compounds; Mixtures
13. Classify as a pure substance or mixture:
a. baking soda (NaHCO3)
b. ice (H2O)
c. iron (Fe) nail
d. a cheese sandwich
Pure
Pure
Pure
Mixture
14. Classify the following pure substances as an element or compound:
a. a silicon (Si) chip
Element
b. oxygen (O2)
Element
c. methane (CH4) in natural gas
Compound
d. rust (Fe2O3)
Compound
15. Classify each of the following mixtures as homogeneous or heterogeneous:
a. fruit salad
Heterogeneous
b. nonfat milk
Homogeneous
c. cranberry juice
Homogeneous
d. tea with lemon slices
Heterogeneous
16. Describe the following properties as chemical or physical:
a. chromium is a steel-gray solid
b. hydrogen reacts readily with oxygen
c. milk will sour when left in a warm room
d. nitrogen freezes at -210oC
e. apple slices turn brown when they are exposed to air
f. propane gas is compressed to a liquid for placement…
Physical
Chemical
Chemical
Physical
Chemical
Physical
17. What type of change, physical or chemical, takes place in each of the following?
a. water vapor condenses to form rain
Physical
b. cesium metal reacts explosively with water
Chemical
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c.
d.
e.
f.
gold melts at 1064oC
sugar dissolves in water
gold is hammered into thin sheets
a silver pin tarnishes in the air
Physical
Physical
Physical
Chemical
18. Suppose we had a mixture of sand, salt and water. Describe how filtration and distillation
could be used sequentially to separate this mixture into the three separate components.
Filter the mixture to remove the sand
Boil off the water to recover the salt
4 Atoms
 Dalton’s atomic theory; Basic atomic structure; isotope symbols; Ions and ionic compounds
19. Write the symbol for each element:
a. Copper
Cu
b. Iron
Fe
c. Lead
Pb
d. Manganese
Mn
20. Write the name for each symbol:
a. I
b. Ag
c. Hg
d. Ni
Iodine
Silver
Mercury
Nickel
21. Identify each as either a metal, nonmetal or metalloid:
a. Calcium
b. Sulfur
c. a shiny element
d. an element that is a gas at room temperature
e. arsenic
f. located in Group 8A
g. a good conductor of electricity
h. boron
Metal
Nonmetal
Metal
Nonmetal
Metalloid
Nonmetal (noble gas)
Metal
Metalloid
22. Identify each description as either a proton, neutron or electron:
a. has the smallest mass
electron
b. carries a 1+ charge
proton
c. is found outside the nucleus
proton and neutron
d. is electrically neutral
neutron
e. has a mass about the same as a proton
neutron
f. is attracted to the protons
electron
23. Indicate whether you would use atomic number, mass number or both to obtain the
following:
a. number of protons in an atom
protons
b. number of neutrons in an atom
both
c. number of particles in the nucleus
mass number
d. number of electrons in a neutral atom
atomic number
24. What is the difference between the mass of an isotope and the atomic mass of an element?
The mass of an isotope is for that isotope alone
The atomic mass is the weighted average of all isotopes of that element
25. Write atomic symbols for isotopes with the following characteristics:
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a.
15 protons and 16 neutrons
31
15
P
b.
35 protons and 45 neutrons
80
35
Br
c.
a chlorine atom with 18 neutrons
35
17
Cl
a mass number of 24 and 13 neutrons
24
11
Na
d.
26. Complete the table:
Element
name
Element
symbol
Atomic
number
Mass
number
# protons
# neutrons
# electrons
Nitrogen
N
7
15
7
8
7
Calcium
Ca
20
42
20
22
20
Strontium
Sr
38
88
38
50
38
Silicon
Si
14
30
14
16
14
Barium
Ba
56
138
56
82
56
27. Is a cation a positive or negative ion? What type of element forms cations, metals or
nonmetals?
Positive – formed by metals
What is the name for the oppositely charged ions? What type of element forms this type?
Anion – formed by nonmetals
28. Predict the formula for the following pairs of ions:
a. Fe3+ and P3FeP
b.
Al3+ and S2-
Al2S3
c.
Fe3+ and O2-
Fe2O3
d.
Mg2+ and Cl-
MgCl2
e.
Na+ and PO43-
Na3PO4
f.
NH4+ and NO3-
NH4NO3
g.
Ca2+ and O2-
CaO
h.
Li+ and N3-
Li3N
5 Nomenclature
 Ionic (known charge, variable charge); Covalent
Name the following compounds:
29. Fe2O3
Iron (III) oxide
30. P2S3
diphosphorus trisulfide
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31. Cu(NO3)2
copper (II) nitrate
32. SnBr4
Tin (IV) bromide
33. Ca3(PO4)2
calcium phosphate
34. Ba(OH)2
barium hydroxide
35. MgCO3
magnesium carbonate
36. PbO
lead (II) oxide
37. NH4NO3
ammonium nitrate
38. BaSO4
barium sulfate
39. K2Cr2O7
potassium dichromate
Write formulas for the following compounds:
40. Sodium hydroxide
NaOH
41. Copper (II) chloride
CuCl2
42. Aluminum phosphate
AlPO4
43. Silicon dioxide
SiO2
44. Magnesium oxide
MgO
45. Sodium carbonate
Na2CO3
46. Cobalt (III) nitrate
CoN
47. Lead (IV) oxide
PbO2
48. Dinitrogen pentoxide
N2O5
49. Iron (II) oxide
FeO
50. Ammonium sulfate
Al2(SO4)3
51. Sulfur hexafluoride
SF6
11 Atomic Theory

EM radiation; Energy emission by atoms; energy levels, orbitals & periodic table; e- configurations
52. Electrons drop to lower energy levels when they _______ (absorb/emit) a photon.
53. What is similar about the following?
a. 5s and 6s orbitals
b. 3p and 4p orbitals
c. 3s and 3p sublevels
both hold 2 electrons
both hold 6 electrons
both in third energy level
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d.
three 3p orbitals
Everything’s the same
54. Indicate the maximum number of electrons in the following:
a. 3s sublevel
2
c.
b. 4p orbital
6
d.
energy level 3
4f sublevel
18
14
55. Draw the abbreviated orbital diagram (arrows) for each of the following:
a.
boron
b.
phosphorus
c.
magnesium
d.
fluorine
-¯
-¯
-¯
-¯
-
-
-
-¯ -¯ -
56. Write complete electron configurations for the following:
a. carbon
1s2 2s2 2p2
b. nitrogen
1s2 2s2 2p3
c. sodium
1s2 2s2 2p6 3s1
d. iron
1s2 2s2 2p6 3s2 3p6 4s2 3d6
57. Write valence electron configurations for the following:
a. calcium
[Ar] 4s2
b. strontium
[Kr] 5s2
c. gallium
[Ar] 4s2 3d10 4p1
d. zinc
[Ar] 4s2 3d10
58. Give the symbol of the element with the each configuration:
a. 1s22s22p4
O
c. 1s22s22p63s23p6 Ar
2
b. [Ne] 3s
Mg
d. [He] 2s22p5
F
59. Give the symbol of the element that meets the following conditions:
a. has 5 electrons in energy level n=3
P
b. has one electron in the 6p sublevel
Tl
c. completes the 7s sublevel
Ra
d. has 4 5p electrons
Te
60. Indicate the number of valence (outermost, s and p) electrons in each of the following:
a. aluminum
3
b. F, Cl, Br and I
7
c. C, Si, Ge, Sn and Pb
4
d. group 8A
8
61. Place the elements in order of decreasing atomic radius
a. Cl, S, P P, S, Cl
b. Ba, Ca, Sr Ba, Sr, Ca
c.
O, S, Se
Se, S, O
62. Arrange each set in order of increasing ionization energy [=energy to remove an electron]
a. O, N, C
C, N, O
b. As, P, N
As, P, N
c. Na, Cl, Al
Na, Al, Cl
d. Na, K, Cs
Cs, K, Na
12 Bonding

Types of bonds; electronegativity; Lewis structures; molecular structures (VSEPR)
63. Determine the number of valence electrons and draw the Lewis (electron dot) structure:
a. CCl4
Tetrahedral
Look these guys up online
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b.
c.
d.
e.
f.
g.
h.
H2S
I2
O2
NH3
NH4+
SO2
CO
Bent
Linear
Linear
Trigonal Pyramidal
Tetrahedral
Bent
Linear
64. Identify the electron domain geometry and the molecular geometry for the molecules and
ion in #63.
Listed above
65. In the molecule PCl3, the four electron groups around the phosphorus atom are arranged in a
tetrahedral geometry. However, the shape of the molecule is called trigonal pyramidal. Why
does the shape of the molecule have a different name from the name of the electron group
geometry?
Don’t worry about this one
66. Describe the following in terms of the electronegativities of the atoms in the bond:
a. ionic bond
Atoms have a large difference in EN
b.
polar covalent bond
Atoms have a medium difference in EN
c.
nonpolar covalent bond
Atoms have no difference in EN
67. Using the periodic table, arrange the atoms in order of increasing electronegativity:
a. Cl, F, Br Br, Cl, F
b. B, O, N B, N, O
c. Mg, F, S
Mg, S, F
8 Moles
 Atomic mass (amu); Molar mass (grams); Avogadro’s number; percent composition of
compounds; empirical formulas; molecular formulas