Download Chemistry Review 1 Answer Key

Chemistry Review 1
TEACHER ANSWER KEY
June 06, 2011
'see explanation below'
1. Base your answer on the information in the accompanying table.
The atomic mass of Cu-63 is expressed to what number of significant figures? [1]
When a measurement greater than or equal to 1 has a decimal point expressed, every number is
counted as a significant figure. Therefore, 62.930 u has 5 significant figures. [1 point]
'see explanation below'
2. Base your answer on the information below.
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to
the pressure on the surface of the liquid. The heat of vaporization of ethanol is 838 joules per gram.
A sample of ethanol has a mass of 65.0 grams and is boiling at 1.00 atmosphere.
Based on Table H, what is the temperature of this sample of ethanol? [1]
Use the vapor pressure curve for ethanol on Reference Table H. The boiling point of ethanol at 1.00
atmosphere is the temperature at which the curve crosses the "101.3 kPa" dashed line. This
temperature is approximately 79oC (+/- 1oC). [1 point]
'see explanation below'
3. Base your answer on the information below.
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to
the pressure on the surface of the liquid. The heat of vaporization of ethanol is 838 joules per gram.
A sample of ethanol has a mass of 65.0 grams and is boiling at 1.00 atmosphere.
Calculate the minimum amount of heat required to completely vaporize this sample of ethanol.
Your response must include both a correct numerical setup and the calculated result. [2]
Use the relevant heat formula on Reference Table T:
One point is awarded for a correct numerical setup, and one point is awarded for a response
consistent with the numerical setup. [2 points]
'see explanation below'
4. Base your answers on the information below.
In a laboratory, a glass tube is filled with hydrogen gas at a very low pressure. When a scientist
applies high voltage between metal electrodes in the tube, light is emitted. The scientist analyzes
the light with a spectroscope and observes four distinct spectral lines. The accompanying table
gives the color, frequency, and energy for each of the four spectral lines. The unit for frequency is
hertz, Hz.
a.On the grid on the answer sheet or on a separate piece of paper, plot the data from the data table
for frequency and energy. Circle and connect the points, including the point (0,0) that has already
been plotted and circled for you. [1]
b. A spectral line in the infrared region of the spectrum of hydrogen has a frequency of 2.3 x 1014
hertz. Using your graph, estimate the energy associated with this spectral line. [1]
a.The correctly drawn graph is shown in the accompanying image:
b. Use the graph in Part a.. A frequency of 2.3 x 1014 Hz corresponds to an energy of: (see equation
in the accompanying image) [1 point]
'see explanation below'
5. Base your answer on the information below.
Carbon and oxygen are examples of elements that exist in more than one form in the same phase.
Graphite and diamond are two crystalline arrangements for carbon. The crystal structure of graphite
is organized in layers. The bonds between carbon atoms within each layer of graphite are strong.
The bonds between carbon atoms that connect different layers of graphite are weak because the
shared electrons in these bonds are loosely held by the carbon atoms. The crystal structure of
diamond is a strong network of atoms in which all the shared electrons are strongly held by the
carbon atoms. Graphite is an electrical conductor, but diamond is not. At 25oC, graphite has a
density of 2.2 g/cm3 and diamond has a density of 3.51 g/cm3.
The element oxygen can exist as diatomic molecules, O2, and as ozone, O3. At standard pressure
the boiling point of ozone is 161 K.
Calculate the volume, in cm3, of a diamond at 25oC that has a mass of 0.200 gram. Your response
must include both a correct numerical setup and the calculated result. [2]
Use the density formula on Reference Table T:
One point is awarded for a correct numerical setup, and one point is awarded for a calculation that
is consistent with the numerical setup. [2 points]
'see explanation below'
6. Base your answer on the information below and the accompanying table.
Bond energy is the amount of energy required to break a chemical bond. The table gives a formula
and the carbon-nitrogen bond energy for selected nitrogen compounds.
State the relationship between the number of electrons in a carbon-nitrogen bond and carbonnitrogen bond energy. [1]
Refer to the given table. As the number of shared electrons in a carbon-nitrogen bond increases, the
bond energy increases. [1 point]
'see explanation below'
7. Based on data collected during a laboratory investigation, a student determined an experimental
value of 322 joules per gram for the heat of fusion of H2O. Calculate the student's percent error.
Your response must include a correct numerical setup and the calculated result. [2]
Use Reference Table B and the percent error formula on Reference Table T: (see image) One point
is awarded for a correct numerical setup, and one point is awarded for a calculation that is
consistent with the numerical setup. The negative sign in the answer is optional. [2 points]
'see explanation below'
8. Base your answer on the information below.
A method used by ancient Egyptians to obtain copper metal from copper(I) sulfide ore was heating
the ore in the presence of air. Later, copper was mixed with tin to produce a useful alloy called
bronze.
Convert the melting point of the metal obtained from copper(I) sulfide ore to degrees Celsius. [1]
Use Reference Table S and the temperature formula on Reference Table T. Copper (Cu, element
29) has a melting point of 1357 K:
K = oC + 273
C = K − 273 = 1357 K − 273 = 1084oC
o
[1 point]
'see explanation below'
9. Base your answer on the information below.
A method used by ancient Egyptians to obtain copper metal from copper(I) sulfide ore was heating
the ore in the presence of air. Later, copper was mixed with tin to produce a useful alloy called
bronze.
A 133.8-gram sample of bronze was 10.3% tin by mass. Determine the total mass of tin in the
sample. [1]
Use the percent composition formula on Reference Table T: (see image)
'see explanation below'
10. Base your answer on the accompanying information.
Convert the boiling point of hydrogen chloride at standard pressure to kelvins. [1]
Use the temperature equation found on Reference Table T:
K = oC + 273 = (–84.9) + (273) = 188 K
[1 point]
'see explanation below'
11. Base your answer on the accompanying information.
Calculate the volume of a tin block that has a mass of 95.04 grams at STP. Your response must
include both a numerical setup and the calculated result. [2]
Obtain the density of tin (Sn, atomic number 50) from Reference Table S. Use this value in the
density equation given on Reference Table T: (see image)
One point is awarded for a correct numerical setup, and one point is awarded for a response
consistent with the numerical setup. [2 points]
'see explanation below'
12. Base your answer on the information below.
Gasoline is a mixture composed primarily of hydrocarbons such as isooctane, which is also known
as 2,2,4-trimethylpentane.
Gasoline is assigned a number called an octane rating. Gasoline with an octane rating of 87
performs the same as a mixture that consists of 87% isooctane and 13% heptane.
An alternative fuel, E-85, can be used in some automobiles. This fuel is a mixture of 85% ethanol
and 15% gasoline.
State the octane rating of a gasoline sample that performs the same as a mixture consisting of 92%
isooctane and 8% heptane. [1]
The octane rating depends primarily on the percentage of isooctane that is equivalent to the
gasoline being rated. If a sample of gasoline is equivalent to a 92% isooctane mixture, its octane
rating is 92. [1 point]
'see explanation below'
13. Base your answer on the information below.
In one trial of an investigation, 50.0 milliliters of HCl(aq) of an unknown concentration is titrated
with 0.10 M NaOH(aq). During the titration, the total volume of NaOH(aq) added and the
corresponding pH value of the reaction mixture are measured and recorded in the accompanying
table.
On the grid provided or on a separate piece of paper, plot the data from the table. Circle and
connect the points. [1]
The graph of pH versus volume is shown in the accompanying diagram:
Credit is awarded for plotting all seven points correctly. (A tolerance of ±0.3 grid space is allowed.)
[1 point]
'see explanation below'
14. Base your answer on the information below.
In one trial of an investigation, 50.0 milliliters of HCl(aq) of an unknown concentration is titrated
with 0.10 M NaOH(aq). During the titration, the total volume of NaOH(aq) added and the
corresponding pH value of the reaction mixture are measured and recorded in the accompanying
table.
Determine the total volume of NaOH(aq) added when the reaction mixture has a pH value of 7.0.
[1]
Use the accompanying graph shown. A pH of 7.0 corresponds to a volume of 25.0 mL (± 0.6 mL).
[1 point]
'see explanation below'
15. Base your answer on the accompanying diagram concerning the classification of matter.
Explain, in terms of particle arrangement, why NaCl(aq) is a homogeneous mixture. [1]
The symbol NaCl(aq) represents an aqueous solution of sodium chloride. All solutions are
homogeneous mixtures. [1 point]
'see explanation below'
16. Base your answer on the accompanying diagram concerning the classification of matter.
Given a mixture of sand and water, state one process that can be used to separate water from the
sand. [1]
Since the sand does not dissolve in the water, the mixture can be separated by filtration, by
decanting the water, or by evaporating the water. [1 point]
'see explanation below'
17. Base your answer on the accompanying diagram concerning the classification of matter.
What type of substance is represented by Z? [1]
Substances are classified as either elements or compounds. Therefore, Z is a compound. [1 point]
'see explanation below'
18. Base your answer on the information below.
The accompanying graph shows a compound being cooled at a constant rate starting in the liquid
phase at 75oC and ending at 15oC.
State what is happening to the average kinetic energy of the particles of the sample between minute
2 and minute 6. [1]
Since the temperature is not changing during this time period, the average kinetic energy of the
particles remains constant. [1 point]
'see explanation below'
19. Base your answer on the accompanying diagram concerning the classification of matter.
What type of mixture is represented by X? [1]
There are two types of mixtures: homogeneous (uniform) and heterogeneous (nonuniform).
Therefore, X is a heterogeneous mixture. [1 point]
'see explanation below'
20. Base your answer on the information below.
The temperature of a sample of a substance is increased from 20.oC to 160.oC as the sample absorbs
heat at a constant rate of 15 kilojoules per minute at standard pressure. The accompanying graph
represents the relationship between temperature and time as the sample is heated.
What is the boiling point of this sample? [1]
Refer to the accompanying graph showing Temperature vs. Time:
The boiling point is the temperature at which boiling occurs: 120oC (± 2oC).
'see explanation below'
21. Base your answer on the information below.
The temperature of a sample of a substance is increased from 20.oC to 160.oC as the sample absorbs
heat at a constant rate of 15 kilojoules per minute at standard pressure. The accompanying graph
represents the relationship between temperature and time as the sample is heated.
In the space provided, or, if taken online, on a separate piece of paper, use the key to draw at least
nine particles in the box, showing the correct particle arrangement of this sample during the first
minute of heating. [1]
Refer to the accompanying graph showing Temperature vs. Time:
During the first minute of heating, the sample is entirely in the solid phase. Diagram A is an
acceptable response:
'see explanation below'
22. Base your answer on the reaction represented by the balanced equation below.
2H2(g) + O2(g) → 2H2O(l )+ 571.6 kJ
Identify the information in this equation that indicates the reaction is exothermic. [1]
An exothermic reaction releases heat. The heat term (571.6 kJ) appears on the right side of the
equation, indicating that this energy is released as the liquid H2O is formed.
'see explanation below'
23. Base your answer on the information below.
The equilibrium equation shown is related to the manufacture of a bleaching solution. In this
equation, Cl-(aq) means that chloride ions are surrounded by water molecules.
In the space on the answer sheet, or, if taken online, on a separate piece of paper, use the key to
draw two water molecules in the box, showing the correct orientation of each water molecule
toward the chloride ion. [1]
Water is a polar molecule; the positive end of the molecule is in the vicinity of the hydrogen atoms.
In solution, the water molecules will align themselves so that the positive ends face the chloride
ion, as shown in the accompanying diagram:
'see explanation below'
24. Base your answer on the information below.
Electroplating is an electrolytic process used to coat metal objects with a more expensive and less
reactive metal. The accompanying diagram shows an electroplating cell that includes a battery
connected to a silver bar and a metal spoon. The bar and spoon are submerged in AgNO3(aq).
Explain why AgNO3 is a better choice than AgCl for use in this electrolytic process. [1]
An electrolytic cell depends on the presence of significant numbers of mobile ions, in this case,
Ag+(aq) ions. See Reference Table F. AgNO3 is soluble in water and would provide the Ag+(aq)
ions that are needed. AgCl, on the other hand, is nearly insoluble in water and would produce
hardly any Ag+(aq) ions.
'see explanation below'
25. Base your answer on the information below.
When a person perspires (sweats), the body loses many sodium ions and potassium ions. The
evaporation of sweat cools the skin.
After a strenuous workout, people often quench their thirst with sports drinks that contain NaCl and
KCl. A single 250.-gram serving of one sports drink contains 0.055 gram of sodium ions.
In the space on the answer sheet or on a separate piece of paper, show a correct numerical setup
for calculating the concentration of sodium ions in this sports drink, expressed as percent by mass.
[1]
Use the percent composition formula on Reference Table T:
% composition by mass = (mass of part)/(mass of whole) × 100%
% composition of Na+ ions = 0.055g / 250.g × 100%
[1 point]
'see explanation below'
26. Base your answer on the information below.
When a person perspires (sweats), the body loses many sodium ions and potassium ions. The
evaporation of sweat cools the skin.
After a strenuous workout, people often quench their thirst with sports drinks that contain NaCl and
KCl. A single 250.-gram serving of one sports drink contains 0.055 gram of sodium ions.
Describe the transfer of energy between the skin and the surroundings as a person perspires and the
sweat evaporates. [1]
As the perspiration evaporates, heat flows from the skin to the surroundings. [1 point]
'see explanation below'
27. Base your answer on the information below.
A portable propane-fueled lantern contains a mesh silk bag coated with metal hydroxides. The
primary metal hydroxide is yttrium hydroxide. When the silk bag is installed, it is ignited and
burned away, leaving the metal hydroxide coating. The coating forms metal oxides that glow
brightly when heated to a high temperature. During a test, a propane lantern is operated for three
hours and consumes 5.0 moles of propane from the lantern's tank. The balanced equation below
represents the combustion of propane.
C3H8 + 5O2 → 3CO2 + 4H2O + energy
At standard pressure, the boiling point of propane is 231 K. In the box on the answer sheet or on a
separate piece of paper, draw a particle diagram to represent the phase of the propane as it leaves
the tank at 294 K. Your response must include at least six molecules. [1]
Propane leaves the tank at a temperature of 294 K, which is higher than its boiling point (231 K).
Therefore, the propane exits the tank as a gas. The particle diagram below represents propane gas
as it leaves the tank:
'see explanation below'
28. Base your answer on the information below.
In a laboratory, a glass tube is filled with hydrogen gas at a very low pressure. When a scientist
applies high voltage between metal electrodes in the tube, light is emitted. The scientist analyzes
the light with a spectroscope and observes four distinct spectral lines. The accompanying table
gives the color, frequency, and energy for each of the four spectral lines. The unit for frequency is
hertz, Hz.
Identify one condition not mentioned in the passage, under which hydrogen gas behaves most like
an ideal gas. [1]
Hydrogen behaves most like an ideal gas at low-pressures and high temperatures. The low-pressure
condition was mentioned in the first sentence of the passage. Therefore, the condition not
mentioned is high temperature. [1 point]
'see explanation below'
29. Base your answer on the information below.
Carbon and oxygen are examples of elements that exist in more than one form in the same phase.
Graphite and diamond are two crystalline arrangements for carbon. The crystal structure of graphite
is organized in layers. The bonds between carbon atoms within each layer of graphite are strong.
The bonds between carbon atoms that connect different layers of graphite are weak because the
shared electrons in these bonds are loosely held by the carbon atoms. The crystal structure of
diamond is a strong network of atoms in which all the shared electrons are strongly held by the
carbon atoms. Graphite is an electrical conductor, but diamond is not. At 25oC, graphite has a
density of 2.2 g/cm3 and diamond has a density of 3.51 g/cm3.
The element oxygen can exist as diatomic molecules, O2, and as ozone, O3. At standard pressure
the boiling point of ozone is 161 K.
Explain, in terms of intermolecular forces, the difference in the boiling points of O2 and O3 at
standard pressure. Your response must include information about both O2 and O3. [1]
O2 has a lower boiling point than O3 because the intermolecular forces between O2 molecules are
weaker than the intermolecular forces between O3 molecules. [1 point]
'see explanation below'
30. Base your answer on the information below.
A piece of magnesium ribbon is reacted with excess hydrochloric acid to produce aqueous
magnesium chloride and hydrogen gas. The volume of the dry hydrogen gas produced is 45.6
milliliters. The temperature of the gas is 293 K, and the pressure is 99.5 kilopascals.
Calculate the volume this dry hydrogen gas would occupy at STP. Your response must include both
a correct numerical setup and the calculated result. [2]
Use the information provided on Reference Table A and the combined gas law formula on
Reference Table T:
One point is awarded for a correct numerical setup, and one point is awarded for a calculation
consistent with the numerical setup. [2 points]
'see explanation below'
31. Identify one ion from Table F that can combine with Pb2+(aq) to produce an insoluble
compound. [1]
According to Reference Table F, any one of the following ions will produce an insoluble
compound when combined with Pb2+(aq): halides (Cl–, Br–, I–), sulfate, carbonate, sulfide,
hydroxide, chromate, phosphate. [1 point]
'see explanation below'
32. Base your answer on the information below.
A 1.0-gram strip of zinc is reacted with hydrochloric acid in a test tube. The unbalanced equation
below represents the reaction.
Zn(s) + HCl(aq) → H2(g) + ZnCl2(aq)
Explain, using information from Reference Table F, why the symbol (aq) is used to describe the
product ZnCl2. [1]
According to Reference Table F, ZnCl2 is soluble in water. [1 point]
'see explanation below'
33. Base your answer on the information below and the accompanying table.
Bond energy is the amount of energy required to break a chemical bond. The table gives a formula
and the carbon-nitrogen bond energy for selected nitrogen compounds.
A 3.2-gram sample of air contains 0.000 74 gram of hydrogen cyanide. Determine the
concentration, in parts per million, of the hydrogen cyanide in this sample. [1]
Use the concentration formula on Reference Table T: (see image)
'see explanation below'
34. Base your answer on the information below.
Biodiesel is an alternative fuel for vehicles that use petroleum diesel. Biodiesel is produced by
reacting vegetable oil with CH3OH. Methyl palmitate, C15H31COOCH3, a compound found in
biodiesel, is made from soybean oil. One reaction of methyl palmitate with oxygen is represented
by the balanced equation below.
2C15H31COOCH3 + 49O2 → 34CO2 + 34H2O + energy
State evidence from the balanced equation that indicates the reaction is exothermic. [1]
In an exothermic reaction, energy is released. The equation shows that energy is a product of the
reaction, which means the reaction is exothermic. [1 point]
'see explanation below'
35. Base your answer on the information below.
A method used by ancient Egyptians to obtain copper metal from copper(I) sulfide ore was heating
the ore in the presence of air. Later, copper was mixed with tin to produce a useful alloy called
bronze.
Calculate the density of a 129.5-gram sample of bronze that has a volume of 14.8 cubic
centimeters. Your response must include a correct numerical setup and the calculated result. [2]
Use the density formula given on Reference Table T: (see image)
One point is awarded for a correct numerical setup, and one point is awarded for a calculation that
is consistent with the numerical setup. [2 points]
'see explanation below'
36. Base your answer on the information below.
Hydrogen peroxide, H2O2, is a water-soluble compound. The concentration of an aqueous hydrogen
peroxide solution that is 3% by mass H2O2 is used as an antiseptic. When the solution is poured on
a small cut in the skin, H2O2 reacts according to the balanced equation below.
2H2O2 → 2H2O + O2
Calculate the total mass of H2O2 in 20.0 grams of an aqueous H2O2 solution that is used as an
antiseptic. Your response must include both a numerical setup and the calculated result. [2]
The equation used to find percent concentration is a slight modification of the percent composition
equation given on Reference Table T: (see image)
One point is awarded for a correct numerical setup, and one point is awarded for a response
consistent with the numerical setup. [2 points]
'see explanation below'
37. Base your answer on the information below.
Heat is added to a sample of liquid water, starting at 80.oC, until the entire sample is a gas at
120.oC. This process, occurring at standard pressure, is represented by the balanced equation below.
H2O(l) + heat → H2O(g)
In the box provided or on a separate piece of paper, using the key, draw a particle diagram to
represent at least five molecules of the product of this physical change at 120.oC. [2]
The product of this reaction is water in the gas phase. Such molecules are widely separated in the
container. See the accompanying diagram:
One point is awarded for showing at least five water molecules, and one point is awarded for
drawing all the particles in the gas phase. [2 points]
'see explanation below'
38. Base your answer on the accompanying information.
Explain, in terms of molecular polarity, why hydrogen chloride is more soluble than methane in
water at 20.oC and standard pressure. [1]
Water is a polar substance, and solubility in it depends on the polarity of the solute. Hydrogen
chloride is polar and is very soluble in water. Methane is nonpolar and is hardly soluble in water. [1
point]
'see explanation below'
39. Base your answer on the accompanying information.
Explain, in terms of intermolecular forces, why ammonia has a higher boiling point than the other
compounds in the table. [1]
The boiling point of a substance depends on the strength of the intermolecular forces present in the
liquid. Since ammonia has a higher boiling point, it must have stronger intermolecular forces than
either liquid methane or liquid hydrogen chloride. [1 point]
4
40. What amount of heat is required to completely melt a 29.95-gram sample of H2O(s) at 0oC?
1. 334 J
3. 1.00 × 103 J
2. 2260 J
4. 1.00 × 104J
4 Use the heat of fusion of ice given on Reference Table B: (see image)
4
41. Which particle diagram shown represents a mixture of element X and element Z, only?
4 Refer to the particle diagrams in this question. Of the choices given, only the diagram in choice
(4) represents a mixture of elements X and Z.
Wrong Choices Explained:
(1) The diagram in choice (1) represents the compound XZ.
(2) The diagram in choice (2) represents a mixture of compounds XZ and X2Z.
(3) The diagram in choice (3) represents a mixture of the compound XZ and of the elements X and
Z.
1
42. An unsaturated aqueous solution of NH3 is at 90.oC in 100. grams of water. According to
Reference Table G, how many grams of NH3 could this unsaturated solution contain?
1. 5 g
3. 15 g
2. 10. g
4. 20. g
1 According to Reference Table G, a saturated solution of NH3 at 90.oC contains 10. grams of NH3
per 100. grams of water. An unsaturated solution at this temperature must contain less than 10.
grams of NH3 per 100. grams of water. Of the choices given, only choice (1) is consistent with this
requirement.
2
43. The accompanying data table gives the temperature and pressure of four different gas samples,
each in a 2-liter container.
Which two gas samples contain the same total number of particles?
1. CH4 and CO2
3. He and CO2
2. CH4 and Ne
4. He and Ne
2 Avogadro's principle states that equal volumes of gases at the same temperature and pressure
contain equal numbers of particles. Of the choices given, only choice (2), CH4 and Ne, meet this
requirement.
3
44. How many total moles of KNO3 must be dissolved in water to make 1.5 liters of a 2.0 M
solution?
1. 0.50 mol
3. 3.0 mol
2. 2.0 mol
4. 1.3 mol
3 Use the molarity (concentration) equation given in Reference Table T:
molarity = [moles of solute]/[liters of solution]
moles of solute = (molarity) • (liters of solution)
= (2.0 M) • (1.5 L)
= 3.0 mol
3
45. Which statement explains why low temperature and high pressure are required to liquefy
chlorine gas?
1. Chlorine molecules have weak covalent
bonds.
3. Chlorine molecules have weak intermolecular
forces of attraction.
2. Chlorine molecules have strong covalent
bonds.
4. Chlorine molecules have strong intermolecular
forces of attraction.
3 At low temperatures and high pressures, the chlorine molecules will be slow enough and close
enough for their weak intermolecular forces to be effective in condensing the gas.
1
46. Given the balanced equation representing a reaction:
CH4(g) + 2O2(g) --> 2H2O(g) + CO2(g) + heat
Which statement is true about energy in this reaction?
1. The reaction is exothermic because it releases 3. The reaction is endothermic because it
heat.
releases heat.
2. The reaction is exothermic because it absorbs
heat.
4. The reaction is endothermic because it absorbs
heat.
1 In this reaction, heat appears as a product. It is released into the surroundings. These types of
reactions are called exothermic.
3
47. Based on bond type, which compound has the highest melting point?
1. CH3OH
3. CaCl2
2. C6H14
4. CCl4
3 High melting points indicate strong chemical bonds such as those found in ionic compounds and
in network covalent substances. Of the following choices, only choice (3), CaCl2 is an ionic
compound. None of the remaining choices are network covalent substances.
1
48. Which property makes it possible to separate the oxygen and the nitrogen from a sample of
liquefied air?
1. boiling point
3. hardness
2. conductivity
4. electronegativity
1 See Reference Table S. The boiling points of nitrogen and oxygen are, respectively, 77K and
90K. As a sample of liquid air is heated to 77K, the nitrogen will boil off, leaving the liquid oxygen
behind.
2
49. Which two substances can not be broken down by chemical change?
1. C and CuO
3. CO2 and CuO
2. C and Cu
4. CO2 and Cu
2 An element cannot be broken down by chemical change. Both C (carbon) and Cu (copper) are
elements.
Wrong Choices Explained:
(1), (3), (4) CO2 and CuO are compounds; compounds can be broken down by a chemical change.
1
50. Which compound is insoluble in water?
1. BaSO4
3. KClO3
2. CaCrO4
4. Na2S
1 See Reference Table F. Of the choices given, only choice (1), BaSO4, is insoluble in water.
3
51. A sample of a gas is contained in a closed rigid cylinder. According to kinetic molecular theory,
what occurs when the gas inside the cylinder is heated?
1. The number of gas molecules increases.
3. The average velocity of the gas molecules
increases.
2. The number of collisions between gas
molecules per unit time decreases.
4. The volume of the gas decreases.
3 According to the kinetic molecular theory, temperature is a measure of the average kinetic energy
of the molecules. Since kinetic energy depends on the velocity, heating a gas will increase the
average velocity of the molecules.
4
52. Solid ZnCl2 and liquid ZnCl2 have different
1. empirical formulas
3. ion ratios
2. formula masses
4. physical properties
4 Solid and liquid ZnCl2 are the same substance in different phases. As such, they have the same
empirical formulas, formula masses, and ion ratios. Their physical properties, however, are
different. For example, a sample of the solid has a definite shape and a definite volume, while a
sample of the liquid has only a definite volume.
3
53. Which phrase describes the molarity of a solution?
1. liters of solute per mole of solution
3. moles of solute per liter of solution
2. liters of solution per mole of solution
4. moles of solution per liter of solution
3 Refer to the molarity formula on Reference Table T. The molarity of a solution is defined as the
number of moles of solute per liter of solution.
4
54. Which substance can not be decomposed by a chemical change?
1. AlCl3
3. HI
2. H2O
4. Cu
4 Only elements can not be decomposed by a chemical change. Of the choices given, only choice
(4), Cu, is an element.
1
55. Tetrachloromethane, CCl4, is classified as a
1. compound because the atoms of the elements
are combined in a fixed proportion
3. mixture because the atoms of the elements are
combined in a fixed proportion
2. compound because the atoms of the elements
are combined in a proportion that varies
4. mixture because the atoms of the elements are
combined in a proportion that varies
1 A compound consists of a chemical combination of two or more elements in which the
composition of each element is fixed. One consequence is that a chemical formula can be written
for the compound (in this case, CCL4).
3
56. When 5 grams of KCl are dissolved in 50. grams of water at 25oC, the resulting mixture can be
described as
1. heterogeneous and unsaturated
3. homogeneous and unsaturated
2. heterogeneous and supersaturated
4. homogeneous and supersaturated
3 Use Reference Table G. The solubility of KCl at 25oC is approximately 34 grams of KCl per 100
grams of H2O. A saturated solution at 25oC containing 50 grams of H2O would contain 17 grams of
KCl. Since only 5 grams of KCl were used to prepare this solution, the solution is unsaturated. By
definition, all solutions are homogeneous mixtures.
2
57. Which aqueous solution of KI freezes at the lowest temperature?
1. 1 mol of KI in 500. g of water
3. 1 mol of KI in 1000. g of water
2. 2 mol of KI in 500. g of water
4. 2 mol of KI in 1000. g of water
2 The solution with the highest concentration of dissolved particles will freeze at the lowest
temperature. Choice (2), 2 mol of KI per 500. g of water, contains the highest concentration since
the solution would contain 4 mol of KI per 1000. g water.
4
58. Which graph represents the relationship between pressure and volume for a sample of an ideal
gas at constant temperature?
4 At constant temperature, the pressure of an ideal gas is inversely proportional to its volume. As
the pressure increases, the volume decreases and vice versa. Of the choices given, only the graph in
choice (4) displays this trend.
3
59. Given the balanced particle-diagram equation:
Which statement describes the type of change and the chemical properties of the product and
reactants?
1. The equation represents a physical change,
with the product and reactants having different
chemical properties.
3. The equation represents a chemical change,
with the product and reactants having different
chemical properties.
2. The equation represents a physical change,
with the product and reactants having identical
chemical properties.
4. The equation represents a chemical change,
with the product and reactants having identical
chemical properties.
3 In the equation shown, one diatomic molecule of element X (the open circles) combines with
three diatomic molecules of element Y (the solid circles) to produce two molecules of compound
XY3 (one open circle and three solid circles). Since the product has a different molecular structure
than that of the reactants, a chemical change has occurred and the product has different chemical
properties than those of the reactants.
1
60. The relatively high boiling point of water is due to water having
1. hydrogen bonding
3. nonpolar covalent bonding
2. metallic bonding
4. strong ionic bonding
1 The relatively high boiling points of substances such as H2O, NH3, and HF are due to the
presence of intermolecular forces known as hydrogen bonding. In order for hydrogen bonding to
occur, hydrogen atoms must be bonded to small, highly electronegative atoms (such as O, N, and
F). As a result, the forces among the molecules of H2O, NH3, and HF are unusually strong and
produce relatively high boiling points.
2
61. Matter is classified as a
1. substance, only
3. homogenous mixture, only
2. substance or as a mixture of substances
4. homogenous mixture or as a heterogeneous
mixture
2 Matter is anything that has mass and volume. This definition includes substances (elements and
compounds) and mixtures of substances.
4
62. Particles are arranged in a crystal structure in a sample of
1. H2(g)
3. Ar(g)
2. Br2(l)
4. Ag(s)
4 A crystal structure is characteristic of the solid phase. Of the choices given, only choice (4),
Ag(s), is in the solid phase.
2
63. Which substance can not be decomposed by a chemical change?
1. ammonia
3. propanol
2. copper
4. water
2 Only elements cannot be decomposed by chemical changes. Of the choices given, only choice
(2), copper, is an element. The other choices are compounds, which can be decomposed by
chemical changes.
1
64. A beaker contains both alcohol and water. These liquids can be separated by distillation
because the liquids have different
1. boiling points
3. particle sizes
2. densities
4. solubilities
1 Distillation is the process by which mixtures of liquids can be separated due to differences in
their boiling points.
3
65. Which term is defined as a measure of the average kinetic energy of the particles in a sample of
matter?
1. activation energy
3. temperature
2. potential energy
4. entropy
3 According to the kinetic-molecular theory (KMT) of matter, the temperature of a sample of
matter is a measure of the average kinetic energy of the particles of the sample.
4
66. How do the boiling point and freezing point of a solution of water and calcium chloride at
standard pressure compare to the boiling point and freezing point of water at standard pressure?
1. Both the freezing point and boiling point of
the solution are higher.
3. The freezing point of the solution is higher
and the boiling point of the solution is lower.
2. Both the freezing point and boiling point of
the solution are lower.
4. The freezing point of the solution is lower and
the boiling point of the solution is higher.
4 When calcium chloride is dissolved in water, the vapor pressure of the solution is lower than the
vapor pressure of pure water. As a result, the solution has a lower freezing point and a higher
boiling point than those of pure water.
3
67. Under which conditions of temperature and pressure does a sample of neon behave most like an
ideal gas?
1. 100 K and 0.25 atm
3. 400 K and 0.25 atm
2. 100 K and 25 atm
4. 400 K and 25 atm
3 Real gases behave most ideally when the volume of the gas particles is negligible and the
particles have enough kinetic energy to overcome intermolecular forces. These occur under
conditions of high temperatures and low pressures. Of the choices given, choice (3), 400 K and
0.25 atm, has the highest temperature and the lowest pressure.
2
68. According to the kinetic molecular theory, which statement describes the particles in a sample
of an ideal gas?
1. The force of attraction between the gas
particles is strong.
3. The collisions between the gas particles
cannot result in a transfer of energy between the
particles.
2. The motion of the gas particles is random and 4. The separation between the gas particles is
straight-line.
smaller than the size of the gas particles
themselves.
2 The following assumptions form the basis of the kinetic-molecular theory:




Intermolecular forces between the gas particles are negligible.
The gas particles move in random, straight-line motion.
All collisions between the gas particles are elastic, that is, energy is conserved.
The separation between the gas particles is much larger than the size of individual particles.
3
69. Which statement describes the transfer of heat energy that occurs when an ice cube is added to
an insulated container with 100 milliliters of water at 25oC?
1. Both the ice cube and the water lose heat
energy.
3. The ice cube gains heat energy and the water
loses heat energy.
2. Both the ice cube and the water gain heat
energy.
4. The ice cube loses heat energy and the water
gains heat energy.
3 Heat represents the transfer of energy from a material at a higher temperature to one at a lower
temperature. Since the temperature of the water is higher than the temperature of the ice cube, heat
energy is lost by the water and gained by the ice cube.
4
70. What is the mass of NH4Cl that must dissolve in 200. grams of water at 50.oC to make a
saturated solution?
1. 26 g
3. 84 g
2. 42 g
4. 104 g
4 Use Reference Table G. At 50oC, the solubility of NH4Cl is 52 grams of solute per 100 grams of
water. In order to saturate 200 grams of water, twice the mass of NH4Cl, 104 grams, must be used.
This problem can also be solved by using the factor-label method: (see image)
2
71. Which element has the greatest density at STP?
1. scandium
3. silicon
2. selenium
4. sodium
2 Use Reference Table S. Of the choices given, choice (2), selenium, has the greatest density at
STP.
2
72. Which gas sample at STP has the same total number of molecules as 2.0 liters of CO2(g) at
STP?
1. 5.0 L of CO2(g)
3. 3.0 L of H2S(g)
2. 2.0 L of Cl2(g)
4. 6.0 L of He(g)
2 Avogadro's hypothesis states that equal volumes of gases at the same temperature and pressure
contain equal numbers of molecules. All of the gases in this question are at STP. In other words,
they are all at the same temperature and pressure. Of the choices given, only choice (2), 2.0 L of
Cl2(g), occupies the same volume as 2.0 L of CO2.
4
73. Which sample has particles with the lowest average kinetic energy?
1. 1.0 g of I2 at 50.oC
3. 7.0 g of I2 at 40.oC
2. 2.0 g of I2 at 30.oC
4. 9.0 g of I2 at 20.oC
4 The average kinetic energy of the particles of a sample depends solely on the temperature of the
sample. The lower the temperature, the lower the average kinetic energy of the particles. Of the
choices given, choice (4), 9.0 g of I2 at 20oC, has the lowest temperature and, therefore, the lowest
average kinetic energy.
4
74. Petroleum can be separated by distillation because the hydrocarbons in petroleum are
1. elements with identical boiling points
3. compounds with identical boiling points
2. elements with different boiling points
4. compounds with different boiling points
4 Distillation is used to separate mixtures that contain substances with different boiling points.
Hydrocarbons are compounds, not elements.
4
75. Which compound is insoluble in water?
1. KOH
3. Na3PO4
2. NH4Cl
4. PbSO4
4 Use Reference Table F. Although sulfates (SO42-) are generally soluble in water, the combination
of this ion with Pb2+ is an exception. PbSO4 is an insoluble compound.
Wrong Choices Explained:
(1), (3) K+ and Na+ are Group 1 ions; their compounds are always soluble in water.
(2) Compounds containing the NH4+ ion are always soluble in water.
4
76. A gas sample is at 25oC and 1.0 atmosphere. Which changes in temperature and pressure will
cause this sample to behave more like an ideal gas?
1. decreased temperature and increased pressure 3. increased temperature and increased pressure
2. decreased temperature and decreased pressure 4. increased temperature and decreased pressure
4 Real gases behave most ideally when their molecules are far enough apart to make their
molecular volumes negligible (low pressure) and are moving fast enough to overcome any
intermolecular forces (high temperature).
2
77. A cylinder with a movable piston contains a sample of gas having a volume of 6.0 liters at 293
K and 1.0 atmosphere. What is the volume of the sample after the gas is heated to 303 K, while the
pressure is held at 1.0 atmosphere?
1. 9.0 L
3. 5.8 L
2. 6.2 L
4. 4.0 L
2 Use the combined gas law equation found on Reference Table T: (see image)
3
78. What is the minimum amount of heat required to completely melt 20.0 grams of ice at its
melting point?
1. 20.0 J
3. 6680 J
2. 83.6 J
4. 45 200 J
3 Use the heat of fusion of ice given on Reference Table B and the heat of fusion equation found on
Reference Table T: (see image)
3
79. Which substance can not be broken down by a chemical change?
1. methane
3. tungsten
2. propanal
4. water
3 Tungsten (atomic number 74) is an element, which cannot be broken down by a chemical change.
Wrong Choices Explained:
(1), (2), (4) Methane, propanal, and water are compounds, which can all be broken down by
chemical changes.
2
80. Object A at 40.oC and object B at 80.oC are placed in contact with each other. Which statement
describes the heat flow between the objects?
1. Heat flows from object A to object B.
3. Heat flows in both directions between the
objects.
2. Heat flows from object B to object A.
4. No heat flow occurs between the objects.
2 Heat flow between two objects depends on their temperatures. Heat flows from the object with
the higher temperature to the object with the lower temperature. Since the temperature of object B
is higher than the temperature of object A, heat will flow from B to A.
3
81. Which unit can be used to express the concentration of a solution?
1. L/s
3. ppm
2. J/g
4. kPa
3 The concentration of a solution can be measured as a percentage (%), as molarity (M), and as
parts per million (ppm).
Wrong Choices Explained:
(1) L/s measures volume flow.
(2) J/g measures heat transfer per unit of mass (such as heat of fusion).
(4) kPa measures pressure.
3
82. Which formula represents a mixture?
1. C6H12O6(l)
3. LiCl(aq)
2. C6H12O6(s)
4. LiCl(s)
3 A solution is a homogeneous mixture. The designation LiCl(aq) represents an aqueous solution of
LiCl.