ANSWERS to
Study Guide for Mrs. Rosenfield’s
Chemistry L2 Midterm Exam 2010-11
Chapter 1 – Introduction to Chemistry – Sections 1.1 & 1.3
Chapter 1 – Sample Problems:
1. What is the purpose of an experiment as part of the scientific method? An experiment is used to
test the hypothesis that a scientist forms as part of the scientific method.
2. Can a theory be proven to be true?
Explain your answer. A theory can only be proven false
because a theory is used to explain a number of conclusions to multiple experiments.
Chapter 2 – Matter and Change – 2.1 – 2.4
Chapter 2 Sample Problems:
1. Which of the following are physical changes?
a. baking cookie dough
c. freezing mercury
b. carving a wooden frame
d. burning wood
No new substances are formed you are only changing the properties of the original
substance, not creating any new substances.
2. Classify each of the following as an element (E), a compound (C) or a mixture (M):
a. silver E
c. spaghetti sauce M
e. river water M
b. alphabet soup M
d. table salt (NaCl) C
f. nitrogen E
3. What is the difference between a heterogeneous mixture and a homogeneous mixture? In a
heterogeneous mixture a person can see that there are different substances that make up
the mixture. Ex: Italian Salad Dressing In a homogeneous mixture you cannot see and
distinguish between the substances that make up the mixture. Ex: Salt water
4. Write the chemical symbol for the following elements:
a. Copper Cu
c. Oxygen O
e. Phosphorus P
b. Silver Ag
d. Sodium Na
f. Helium He
5. Write the name of the element for the following chemical symbols:
a. Ca Calcium
c. F Fluorine
e. Au Gold
b. S Sulfur
d. K Potassium
f. Cl Chlorine
6. Classify the following as either homogeneous (homo) or heterogeneous (hetero) mixtures.
a. Italian salad dressing hetero
c. black coffee homo
b. chocolate chip ice cream hetero
d. orange juice without pulp homo
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Chapter 3 – Scientific Measurement – Sections 3.1 – 3.5
Chapter 3 Sample problems:
1. Classify each statement as either qualitative or quantitative.
a. The ball is large
qualitative
b. The diameter of the ball is 31 centimeters
quantitative
c. The air pressure in the ball is 12 pounds per square inch
quantitative
d. The surface of the basketball is rough
qualitative
2. Determine the number of significant figures in each of the following numbers:
a. 12 basketball players
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b. 0.010 square meters
2
3. Round each measurements to three significant figures:
a. 98.473 L
98.5 L
b. 0.000 763 21 cg 0.000763 cg
4. What is the symbol and meaning of each prefix?
a. milli-
m-
1000x smaller
c. kilo-
k-
1000x larger
b. mega-
M-
1 millionx larger
d. centi-
c-
100x smaller
5. Name the quantity measured by each of the following units and give the symbol of the unit.
a. kilogram
mass, kg
b. cubic centimeters volume, cm3
c. meter
length, m
d. second
time, s
6. A plastic ball with a volume of 19.7 cm3 has a mass of 15.8 g. What is its density?
D = mass/volume = 15.8g/19.7cm3 = 0.802 g/cm3
7. In a lab experiment, the density of gold was measured as 18.5 g/cm3. The best accepted value is
19.3 g/cm3. What is the percent error in the lab measurement?
 accepted  measured 
 19.3g / cm3  18.5 g / cm3 
% Error = 
 *100  
 *100  4.15%error
accepted
19.3g / cm3




This result is good based on the fact that errors under 5% are acceptable for most experiments.
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Chapter 4 – Problem Solving in Chemistry – Sections 4.2-4.3
Chapter 4 Sample Problems:
For the following problems state what is given, state the unknown and write the equation that you will use
to find the answer:
1. A small piece of gold has a volume of 1.35 cm3.
a. What is the mass, if the density of gold is 19.3 g/cm3.
Given: volume = 1.35 cm3, density =19.3g/cm3
Unknown: mass
Equation: d=m/v  m=d*v=(19.3g/cm3)(1.35cm3) Answer: 26.1 g
b. What is the volume of 215 grams of gold? (Use the density above).
Given: mass = 215 g, density = 19.3g/cm3
Unknown: volume
Equation: v = m/d = (215g/19.3g/cm3)
Answer: 11.1 cm3
2. Make the following conversions. Show your calculations and write the units.
a. 36 cm to meters
Answer: 0.36 m
b. 3.72 x 10-3 kg to grams
Answer: 3.72 g
c. 0.0371 m to kilometers
Answer: 3,71 x 10-5 km
Chapter 5 – Sections 5.1 – 5.4
Chapter 5 Sample Problems:
1. Complete each row in the following tables: (The second table may have either atoms or ions)
Electron
Charge
-1
Relative Mass
0 amu
Proton
+1
1 amu
Location in atom
Electron
Cloud
Nucleus
Neutron
0
1 amu
nucleus
Symbol
Atomic
number
Mass
number
Protons
Neutrons
Electrons
39
19K
19
39
19
20
19
51
2+
23V
23
51
23
28
21
16
28O
8
16
8
8
10
3
2. Identify each element as a metal (M), nonmetal (NM) or semimetal/metalloid (SM):
a. calcium M
b. silicon SM
c. manganese M
d. sulfur NM
3. Name two ways in which isotopes of an element differ. Isotopes differ in the number of neutrons
that are in the nucleus and the mass number.
4. If element X had one isotope with mass 44.0 amu and abundance of 75.0%, and a second isotope
with mass 46.0 amu and abundance of 25.0%, what would the atomic mass of X be?
Atomic mass = (44.0amu x 0.75) + (46.0amu x 0.25) = 44.5 amu
Chapter 13 – Electrons in Atoms (Omit Pg 370 – Exceptional Electron Configurations)
Equations given on exam: c = 
E = h
c = 3.00 x 108 m/s
h = 6.626 x 10-34 J s
Sample Problems:
1. Write the number of orbitals and write the maximum number of electrons that can be in the following
families of orbitals.
a. 3p 3, 6
b. 2s 1, 2
c. 4f 7, 14
d. 3d 5, 10
2. Write the complete electron configuration for each atom:
a. Lithium
1s22s1
b. Phosphorus 1s22s22p63s23p3
3. Write the electron configuration using the noble gas abbreviation:
a. Sodium
[Ne]3s1
b. Mercury
[Xe]6s24f145d10
4. Give the symbol and name for the atom that corresponds to each electron configuration:
a. 1s2 2s2 2p4
O, oxygen
b. [Ar] 4s1
K, potassium
5. A photon has a wavelength of 6.56 x 10-7 m, what is the frequency of the light?
Given: =6.56x10-7 m
Unknown: frequency, 
Equation:  = c(3.00x108m/s)/( 6.56x10-7 m)
Answer: 4.57 x 1014 Hz
6. What is the energy of a photon of green light with a frequency of 5.80 x 1014 Hz?
Given:  = 5.80 x 1014 Hz
Unknown: Energy
Equation: E=h = (6.63x10-34 Js)( 5.80 x 1014 Hz)
Answer: 3.85x10-19J
Chapter 6 – Chemical Names and Formulas – Sections 6.1 – 6.6
Chapter 6 Practice Problems:
1. Write the symbol and name for the ion formed by:
a. A potassium atom
K+1
potassium ion
b. An aluminum atom
Al3+
aluminum ion
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c. A fluorine atom
F-1
fluoride
d. A nitrogen atom
N-3
nitride
2. Write the formula (including charge) for each polyatomic ion:
a. Hydroxide OH-
b. Nitrate NO3-
c. Sulfate SO42-
3. Write the formulas for these ionic compounds:
a. Potassium sulfate K2SO4
c. Magnesium hydroxide Mg(OH)2
b. Silver(I) chloride AgCl
d. Iron(III) oxide Fe2O3
4. Name the following ionic compounds:
a. NaI sodium iodide
b. K2S potassium sulfide
b. NH4Br ammonium bromide
c. Cu2O copper (I) oxide
5. Write the formula or name these molecular compounds:
a. CS2 carbon disulfide
c. carbon tetrabromide CBr4
b. Diphosphorus trioxide P2O3
d. N2O5 dinitrogen pentoxide
6. Explain how to tell if a compound is ionic or molecular from the name (or formula)?
A compound is ionic when you have a metal and a nonmetal element bonded together and it is
covalent when you have two or more nonmetals bonded together.
7. In the name of a compound, when and why are Roman numerals used? Roman numerals are
used when you have metals that can have more than one charge. The Roman numerals tell
you what the actual charge on the ion is in the compound.
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