AP Chemistry
Midterm Exam Practice Questions
Part I—Multiple Choice.
1) What is the molecular structure of IF5 and what is the bond angle between the atoms?
a. square pyramidal—<90°, <180°
b. square pyramidal—90°, 180°
c. trigonal bipyramidal—<90°, <180°
d. square planar—90°, 180°
2) Which of the following has the shortest CO bond?
a. CO32b. CO2
c. CO
d. C2H5OH
3) Which element has the greatest 2nd ionization energy?
a. Strontium
b. selenium
c. potassium
d. tungsten
4) Which is matched incorrectly?
a. HNO3—nitric acid
b. H2SO4—sulfuric acid
c. ClO4-—perchlorate ion
d. Cu(NO3)2—copper nitrate
5) What phenomenon occurs when electrons are ejected from metals when hit by light?
a. London dispersion forces
b. photoelectric effect
c. oxidation
d. hydrolysis
6) Which of the following does NOT form sp3d hybrid orbitals?
a. BrF3
b. XeF2
c. ICl5
d. [ClF4]+
7) The critical temperature of a substance is the
a. Temperature at which the vapor pressure of the liquid equals external pressure
b. Temperature at which the vapor pressure of the liquid equals 760 mm Hg
c. Temperature at which the solid, liquid, and vapor phases are in equilibrium
d. Lowest temperature above which a substance can’t be liquefied at any pressure
8) Which type of spectroscopy does not use a type of EM radiation as an energy source?
a. UV-Vis spectroscopy
b. Mass spectrometry
c. IR spectroscopy
d. Photoelectron spectroscopy (PES)
9) Which of the following compounds is polar?
a. C2H4
b. SeF6
c. CH3OH
d. BF3
10) Which pair of scientists and their discoveries is incorrect?
a. Robert Millikan—determined the charge and mass of an electron
b. Ernest Rutherford—used alpha particles to determine a proton’s charge
c. James Chadwick—used alpha rays to discover neutrons
d. Dmitri Mendeleev—discovered a way to systemize elements in a table
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11) Which statement is FALSE about the following reaction?
C(s) + O2(g)  CO2(g)
a. 16 g of O2 will produce 44 g of CO2
b. 12 g of C will produce 44 g of CO2
c. 1 molecule of C and 1 molecule of O2 will produce 1 molecule of CO2
d. 1 mole of oxygen will produce 44 g of CO2
12) In an endothermic reaction, as the temperature of a solution is increased, what happens?
a. The solubility of the solute increases.
b. The solubility of the solute stays the same.
c. The density of the solution increases.
d. The density of the solution stays the same.
13) What happens when aluminum metal is placed in cold water?
a. Aluminum hydroxide is formed.
b. Hydrogen gas is released.
c. Both aluminum hydroxide and hydrogen gas are formed.
d. No reaction occurs.
14) A 1.0-L sample of gas at 27°C and 1.0 atm of pressure is subjected to a decrease in
pressure and an increase in temperature. Which of the following happens to its density?
a. It increases.
b. It decreases.
c. It cannot be determined with the given information.
d. It varies depending on the type of gas.
15) Which of the following ions or atoms does not fit?
a. Clb. K+
c. Mg2+
d. Ar
16) Which of the following does NOT have a pi bond?
a. CO
b. NO-2
c. NO3-
d. All of these have one
17) What is the sum of the coefficients for the decomposition of magnesium chlorate?
a. 5
b. 8
c. 3
d. 10
e. 2
18) Which test would NOT be helpful to determine the type of solid in a lab?
a. melting point
b. malleability
c. conductivity
d. color
19) Which element has the largest atomic radius?
a. P
b. S
c. O
d. Ne
20) The configuration [Ar]4s23d104p5 belongs to which element?
a. barium
b. bromine
c. chlorine
d. beryllium
21) Which one of the following is a network solid?
a. CaO
b. SiO2
c. ice
d. Na
22) A 0.100 mol sample of NO(g) and a 0.100 mol sample of O 2(g) are added into a 1.000 L
flask where a reaction occurs to produce NO2(g). What is the mole fraction of oxygen in
the flask assuming the reaction goes to completion?
a. 1.000 b. 0.667
c. 0.500
d. 0.333
e. 0.200
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23) What is the average atomic mass of element X based on the following data:
Isotope
48 X
50 X
a. 49.0
Atomic mass, amu
48.0
50.0
b. 49.5 amu
Percent Abundance
10.0
90.0
c. 49.8 amu
d. 50.0 amu
24) The particulate model at right is a representation of a
mixture of
a. an element and a compound.
b. atoms and molecules.
c. four different atoms.
d. two different compounds.
25) Name the element whose mass spectrum is shown below.
a. germanium
b. selenium
c. sulfur
d. fermium
26) Which of the following is added to silicon to enhance its properties as a semiconductor?
a. Pb
b. Ca
c. Zn
d. As
27) Which type of alloy and which type of doping would be present in the situation described
in question 26?
b. substitutional alloy; N-type doping
c. interstitial alloy; N-type doping
c. substitutional alloy; P-type doping
d. interstitial alloy; P-type doping
Part II—Short Answer.
28) Interpret each of the following four examples using modern bonding principles:
a. C2H2 and C2H6 both contain two carbon atoms. However, the bond between the
two carbon atoms in C2H2 is significantly shorter than that between the two
carbons in C2H6.
b. The bond angle in the hydronium ion, H3O+, is less than 109.5°, the angle of a
tetrahedral molecule.
c. The lengths of the bonds between the carbon and the oxygens in the carbonate
ion are all equal and are longer than one might expect to find in the carbon
monoxide molecule.
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d. The CNO- ion is linear.
Volume (L)
29) Answer the following questions about NH3 and methane, CH4. Assume that both gases
exhibit ideal behavior.
a. Draw the complete Lewis structure for the two molecules.
b. Identify the shape of each molecule.
c. One of the gases dissolves readily in water to form a solution with a pH above 7.
Identify the gas and account for this observation by writing a chemical equation.
d. A 1.5 mol sample of methane gas is placed in a piston at constant temperature.
Sketch the expected plot of volume vs. pressure, holding temperature constant.
Pressure (atm)
e. Samples of ammonia and methane gas are placed in 2-L containers indicated in
the diagram below:
i. Indicate whether the average kinetic
energy of the ammonia molecules is
greater than, equal to, or less than the
average kinetic energy of the methane
molecules. Justify your answer.
ii. Indicate whether the root mean square
speed of the methane molecules is
greater than, equal to, or less than the root mean square speed of the
ammonia molecules. Justify your answer.
iii. Indicate whether the number of ammonia molecules is greater than, equal to,
or less than the number of methane molecules. Justify your answer.
30) Explain each of the following in terms of (1) inter and intra-atomic or molecular forces and
(2) structure.
a. ICl has a boiling point of 97°C whereas NaCl has a boiling point of 1400°C.
b. KI is very soluble in water whereas I2 has a solubility of only 0.03 g per 100 g of
water.
c. Solid Ag conducts an electric current whereas solid AgNO3 does not.
d. PCl3 has a measurable dipole moment whereas PCl5 does not.
e. The carbon-to-carbon bond energy in C2H5Cl is less than it is in C2H3Cl.
31) Bromine reacts with a metal (M) as follows: M(s) + Br2(l)  MBr2(s).
a. Describe the type of bonding that would occur in MBr 2.
b. Define lattice energy. What factors would affect the lattice energy of MBr 2?
c. If metal M were either magnesium, beryllium, or calcium, arrange the possible
compounds in order of increasing lattice energies.
d. If metal M were either magnesium, sodium, or aluminum (the equations would be
different), arrange the resulting compounds in order of increasing lattice energy.
Explain your reasoning.
e. Explain how the heat of the reaction is affected by the ionization energy for the
metal, M.
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32) The first three ionization energies (I1, I2, I3) for beryllium and neon are given in the
following table:
(kJ/mole)
I1
I2
I3
Be
900
1757
14,840
Ne
2080
3963
6276
a. Write the complete electron configuration for beryllium and for neon.
b. Draw the Lewis diagrams for Be and Ne.
c. Explain any trends or significant discrepancies found in the ionization energies
for beryllium and neon.
d. If chlorine gas is passed into separate containers of heated beryllium and heated
neon, explain what compounds (if any) might be formed, and explain your
answer in terms of the electron configurations of these two elements.
e. An unknown element X has the following three ionization energies:
(kJ/mole)
I1
I2
I3
X
419
3069
4600
On the basis of the ionization energies given, what is most likely to be the
compound produced when chlorine reacts with element X and explain your
reasoning.
33) Answer each of the following using appropriate chemical principles.
a. Why does it take longer to cook an egg in boiling water at high altitude than it
does at sea level?
b. Dimethyl ether CH3OCH3 is not very soluble in water but ethanol CH3CH2OH is
miscible with water. Which of these two structural isomers is more volatile?
c. At ordinary conditions, HF (normal boiling point = 20°C) is a liquid, whereas HCl
(normal boiling point = -114°C) is a gas.
d. The N—O bonds in NO2- are equal in length, whereas they are unequal in HNO2.
34) For each reaction, in part (i) write a BALANCED equation and in part (ii) answer the
question about the reaction. In part (i), coefficients should be in terms of lowest whole
numbers. Assume that the solutions are aqueous unless otherwise indicated. Represent
substances in solutions as ions if the substances are extensively ionized. Omit formulas
for any ions or molecules that are unchanged by the reaction.
Example: A strip of magnesium is added to a solution of silver nitrate. Which substance is
oxidized in the reaction?
(i)
Mg + 2Ag+  Mg2+ + 2Ag
(ii)
Magnesium was oxidized.
a. Water is added to a flask of solid sodium oxide. What type of reaction is this?
b. A dilute solution of sulfuric acid is added to a solution of barium chloride. Identify
the spectator ions in the reaction mixture.
c. A solution of hydrogen peroxide is warmed. What is the oxidation number of the
oxygen before and after the reaction?
d. Finely ground aluminum is added to a solution of copper (II) sulfate. Which
species was oxidized in this reaction?
e. Manganese dioxide (acting as a catalyst) is added to a solid sample of potassium
chlorate and the mixture is then heated. How does a catalyst increase the rate of
a reaction?
f. Solid calcium oxide is added to silicon dioxide and the mixture is heated strongly.
What is the name of the product?
g. Hydroiodic acid is mixed with solid calcium carbonate. What is the driving force
of this reaction?
h. Copper (II) sulfate pentahydrate is strongly heated. Explain the term “hydrate”.
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35) Propane C3H8 is a hydrocarbon that is commonly used as a cooking fuel.
a. Write a balanced equation for the complete combustion of propane gas.
b. Calculate the volume of air at 30°C and 1.00 atmosphere that is needed to burn
completely 10.0 grams of propane. Assume that air is 21.0 percent O 2 by
volume.
c. The heat of combustion of propane is -2,220.1 kJ/mol. Calculate the heat of
formation of propane given that ∆Ho of H2O(l) = -285.3 kJ/mol and ∆Ho of CO2(g)
= -393.5 kJ/mol.
d. Assuming that all of the heat evolved in burning 30.0 grams of propane is
transferred to 8.00 kilograms of water (specific heat = 4.18 J/g°C), calculate the
increase in temperature of the water.
36) A sample of dolomitic limestone containing only CaCO 3 and MgCO3 was analyzed.
a. When a 0.2800 gram sample of this limestone was decomposed by heating, 75.0
milliliters of CO2 at 750 mm Hg and 20°C were evolved. How many grams of
CO2 were produced?
b. Write equations for the decomposition of both carbonates described above.
c. It was also determined that the initial sample contained 0.0448 gram of calcium.
What percent of the limestone by mass was CaCO3?
d. How many grams of the magnesium-containing product were present in the
sample in (a) after it had been heated?
37) Elements can be distinguished by their PES spectrum.
a. Identify the element represented by the spectrum below. Write the element’s
electron configuration.
b. The above spectrum contains three peaks labeled with the number two. Identify
each of these peaks. What cause the energy values to differ?
c. Can PES be used to identify compounds? Why or why not?
d. Do you expect this element to be paramagnetic or diamagnetic? Explain.
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