Chemistry – Review for 1st Semester Exam Key
I. Measurement and Calculations:
1. Demonstrate understanding of the use of measurements in science.
You should be able to apply the rules of significant figures to choose answer with
the correct number of significant figures.
Express the answer in the correct number of significant figures. Label with
appropriate units.
a. 21.3 g = 16.384615
1.3 cm3
16 g/cm3
b. 6.34 cm2 x 1.2 cm
1.217 cm
6.3 cm2
= 6.251437
c. 13.21m x 61.5 m = 812.415
812 m2
d. 21.50 cm = 2.529411765
2.53 cm/in
8.50 in
You should also be able to measure the length of an object or volume of a liquid to
the appropriate number of significant figures based upon the measuring
instrument.
2. Which of the following best expresses the width of the business card?
a. 5 cm
b. 5.0 cm
c. 5.05 cm
d. 5.50 cm
Demonstrate proficiency in the use of scientific notation and use of dimensional
analysis (factor label) in metric conversions.
Know the meaning of the following metric prefixes and be able to make
conversions utilizing them.: milli-, centi-, kiloExample:
1m
 0.15m
1000mm
3. Complete the indicated conversions:
150mm 

a. 37 g x 1000mg/1g =
37000 mg
c. 138 m x 1km/1000m = 0.138 km
b. 4.7 kg x 1000g/1kg =
4700 g
d. 4021 mm x 1m/1000mm =
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4.021 m
1st Sem Review-v2.2
4. Be able to convert standard notation to scientific notation and vice versa.
standard
scientific
1300
1.3x103
0.00155
1.55x10-3
1680000
1.68 x 106
0.0273
2.73 x 10-2
5. Determine the density of an object from a data table or from a graph of mass vs
volume. Data table average is 7.8 g/cm3
Volume (cm3)
1.5
3.0
4.5
6.0
7.5
9.0
Mass (g)
11.7
24.0
35.1
48.0
58.5
70.0
6. Plot the data above and determine
the density of the substance.
Slope should be about 7.8 g/cm3
7. What volume would 150g of the
substance occupy? Show work; use
labels.
150g x 1mL/7.8g = 19mL
8. Correctly state the law of conservation of mass.
Mass is neither created nor destroyed by only rearranged in any chemical
or physical process.
9. If 41g of salt are dissolved in 202g of water what will be the resulting mass?
41g + 202g = 243 g total
II. Gases and Kinetic Theory
1. Use arrows to identify the relationship between P and T, V and T, P and n
and P and V. ↑P↑T (Gay-Lussac’s); ↑V↑T (Charles’); ↑P↑n (Diver’s);
↑P↓V (Boyle’s)
2. Identify the law associated with each of the above variables.
You should be able to identify the correct graphic representation of the relationships
between volume, temperature, and pressure.
3. Which graph describes the relationship between gas pressure and volume? D
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4. Which graph (previous page) describes the relationship between gas
pressure and temperature?A
5. What temperature scale is used when working with gases? Kelvin
Solve problems given volume, pressure, or temperature of gases.
6. A sample of carbon dioxide has a volume of 2.0 L at a temperature of –10˚C
(263K). What volume will this sample have when the temperature is
increased to 110˚C (383K). Assume that the pressure does not change and
that no carbon dioxide leaks from the sample. (Use the grid!)
↑V↑T
2.0L x 383K/263K = 2.9L
7. A 12.7 L sample of gas is under a pressure of 740 mm Hg (0.974atm) at
20°C (293K). What will be the volume of the gas if the pressure increases to
1.00 atm (760mmHg) and the temperature drops to 0.0°C (273K)?
↑P↓V; ↓V↓T
12.7L x 0.974atm/1atm x 273K/293K = 11.5 L
or
12.7L x 740mmHg/760mmHg x 273K/293K = 11.5 L
8. What is the
pressure in
the bulb for a
and b
A = 787 mmHg
B = 660 mmHg
III. The role of energy in physical change
1. Describe the ways energy is stored in solids, liquids and gases.
 Thermal energy – energy of motion – related to the absolute temperature
Hotter molecules move more rapidly than slower ones; for a given volume the gas
will have a greater pressure due to the greater number of
 Phase energy – energy due to attractions between molecules; the stronger the
attractions, the lower the energy of the system of particles
Lowest for solids, greater in liquids, greatest in gas phase
 Heat is the transfer of energy into or out of a system due to molecular collisions.
Energy is transferred from hotter (faster) molecules to colder (slower) molecules.
2. Explain why the alcohol level in a thermometer rises when it is placed in a
warmer fluid. (3-step process)
-Energy transfers into the thermometer
-Alcohol particles speed up and collide more/harder with eachother
-Alcohol expands, raising the level in the thermometer
3. Describe what happens (at the molecular level) when a glass of cold water
warms up to room temperature.
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1st Sem Review-v2.2
Draw energy bar graphs to account for energy storage and transfer in all sorts of
changes. (review ws 1 and 2, quiz in unit 3).
4. A tray of water at 22°C is put in the freezer and cools to -8.0°C
When energy is transferred to a sample of matter, either the particles speed up
(temperature increases) or they get pulled apart (phase change), but not both at
the same time. This helps account for the shape of the warming curve you got in
the Icy Hot lab.
5. On the graph above label which phases are present in each portion of the curve.
6. Label the sections where the thermal energy (Eth) of the sample is changing.
7. Label the sections where the interaction energy (Ei) is changing.
Use the equations Q  mH, where H f  334 J
J to determine the energy
g , Hv  2260 g
transferred to or from water during a phase change. Use Q  mct and c  4.18 J
gÞC
to determine the energy transferred to or from water during heating or cooling.

8. What is the energy required to heat 100. g coffee from 25°C to 91.°C. (Show

work)
Q = 100.g x 4.18J/gC x (91-25C) = 27600J
9. How much energy is released when 75.0 g of water cools from 30°C and ends up
completely frozen at 0°C. (Show work)
Q = 75.0 g x 4.18J/gC x (30-0C) = 9400J
Q = 75.0 g x 334J/g = 25100J
25100J + 9400J = 34500J total
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1st Sem Review-v2.2
IV. Mixtures and Compounds
Describe how matter is organized.
1. You should be able to identify diagrams and distinguish between atoms,
molecules, compounds, mixtures, gases, and solids.
a.
What is represented in Figure A?
Atoms of an element
b.
Does Figure B represent a compound or an element? Explain.
Element- everything in each molecule is the same element
c.
Which diagrams show only molecules? What is different about the
molecules represented by the diagrams? B (element), C (compound),
D (mixture of an element and compound)
2. Mixtures can be separated by _Physical____ means and compounds can be
separated by __Chemical_______ means.
3. State Avogadro’s hypothesis.
Equal volumes contain equal quantities (if same conditions), from this you
can deduce that some elements must be diatomic and their relative masses.
4. If two equal volumes of gas A and B are combined (same temp and pressure),
how many volumes of product will be formed (1). Assume A and B are
monatomic and draw the above reaction. (1 volume created from 2
reactants)
5. Draw the reaction above is gas A and B are diatomic. (2 volumes created)
6. List the 7 diatomic molecules. Br, I, N, Cl, H, O, F
7. State the Law of Constant Composition and the Law of Multiple Proportions
Constant composition: the same compound will have a constant and
unchanging whole number proportion of elements. Multiple Proportions:
same elements may form different compounds with different whole number
ratios.
V. The mole concept and chemical reactions
Recognize that atoms are too small to count directly. We determine how many
there are in a sample by finding their mass. We use the mole to determine the
number of atoms and molecules. Molar mass (on Periodic Table) is relative mass,
based originally on hydrogen (lightest element).
1. Calculate the molar mass of the compounds below:
Pb(NO3)2
BaSO4
331.22 g/mol
233.4 g/mol
Determine the number of atoms or moles using Avogadro’s number and the molar
mass of a compound.
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1st Sem Review-v2.2
2. Solve the following using molar mass, Avogadro’s number or both:
a. 12 g MgCl2 x 1 mol/95.21g
=
0.13
b. 3 moles NaCl x 6.02x1023 atoms/1 mol
=
moles MgCl2
2.0x1024
atoms Cl
c. 12.0g of PbSO4 xmol/303.27g x6.02x1023molec./mol= 2.38x1022 molecules
Determine the empirical and molecular formulas from data.
3. A compound is composed of 7.20 g of carbon, 1.20 g of hydrogen, and 9.60 g of
oxygen. The molar mass of the compound is 180 g. Find the empirical and
molecular formulas for this compound.
7.20g C = 0.600 mol C
1.20g H = 1.20 mol H
9.60g O = 0.600 mol O
E = CH2O
180g/30.03g = 6
M = C6H12O6
Be able to distinguish between the meaning of coefficients and subscripts in a balanced
chemical equation.
4. Draw pictures to represent the balanced equation:
Ba
+
2HCl --> BaCl2
+
H2
VI. Matter and Atomic Theory
1. How does Thomson’s model of the atom differ from Dalton’s.
Plum Pudding- has mobile negatives (electrons)
Distinguish between insulators and conductors:
2. Give an example of an insulator and a conductor.
I = Paper
C = Aluminum Foil
3. Draw a picture of an insulator exposed to a positively charged object
Electrons towards object, but remain inside their atoms
4. Draw a picture of a conductor exposed to a negatively charged object.
Electrons away from object, and leave individual atoms
5. Define polarization
Movement of electrons in an atom to create slightly charges sides
Distinguish between molecular and ionic solids.
Molecular solids (formed from atoms of non-metals) exist as separate molecules
that attract one another. When dissolved in water, the solution does NOT conduct
electricity; e.g., C6H12O6.
Ionic solids (formed from metal and non-metals) exist as a lattice of charged
particles (ions). The formula represents the simplest integer ratio (empirical
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1st Sem Review-v2.2
formula) of the ions; e.g. CaCl2. When dissolved in water, the solution conducts
electricity.
Demonstrate knowledge of the meaning of a chemical formula in terms of atoms and
molecules.
6. Given the formula of a compound, identify the number of atoms present.
a. Pb(NO3)2
c. Al2(SO4)3
b. Na3PO4
9
8
17
7. Name ionic and molecular compounds from formulas and vice versa.
Write the formula of binary compounds (formed from two kinds of atoms).
a potassium iodide
KI
b. nitrogen dioxide
NO2
c. sodium oxide
Na2O
d. aluminum chloride
AlCl3
d. tin(IV) chloride
SnCl4
f. iron(III) sulfide
Fe2S3
g. phosphorus tribromide
PBr3
8. Write the name of binary compounds (formed from two kinds of atoms).
a. SnO
tin (II) oxide
b. SnBr4
tin (IV) bromide
c. SO2
sulfur dioxide
d. Al2O3
aluminum oxide
e. NCl3
nitrogen trichloride
f. CaO
calcium oxide
9. Write the formula or name of compounds formed from polyatomic ions.
a. calcium nitrate
Ca(NO3)2
b. potassium phosphate
K3PO4
c. aluminum acetate
Al(C2H3O2)3
d. ammonium sulfate
(NH4)2SO4
e. Al(OH)3
Aluminum hydroxide
f. Cu2SO4
copper (I) sulfate
g. (NH4)2CO3
ammonium carbonate
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1st Sem Review-v2.2