AP Chemistry Exam #2
Thermochemistry, Atomic Theory, Periodic Properties
Part I: Select the best choice and mark your answer on the answer section on the
cover page for this exam. Each question is worth 1 point.
1. Which of the following has a standard enthalpy of formation that is not zero?
(A)
(B)
(C)
(D)
(E)
Na (s)
Hg (l)
H2O (l)
N2 (g)
C (s)
2. The element with the ground state electron configuration of [Ar] 4s23d7 is:
(A)
(B)
(C)
(D)
(E)
Mg
K
Ar
Co
Ni
3. The number of unpaired electrons in a groundstate chromium atom is:
(A)
(B)
(C)
(D)
(E)
1
2
3
4
5
4. The correct ordering of atoms in progressively decreasing ionization energy is:
(A)
(B)
(C)
(D)
(E)
F > O > C > Li > Na
Na > Li > C > O > F
F > O > C > Na > Li
C > O > F > Li > Na
O > F > C > Na > Li
5. Which set of quantum numbers is not acceptable? (n, l, ml, ms)
(A)
(B)
(C)
(D)
(E)
(4, 3, -2, +1/2)
(3, 0, 1, -1/2)
(3, 0, 0, -1/2)
(3, 1, 1, +1/2)
(2, 0, 0, -1/2)
6. It may be correctly stated that isotopes:
(A) contain the same number of electrons but differ in mass due to the number of
neutrons.
(B) contain the same number of protons but differ in mass due to the number of neutrons.
(C) contain the same number of neutrons but differ in mass due to the number of
electrons.
(D) contain a different number of protons.
(E) contain the same number of protons and neutrons but never the same number of
electrons.
7. The correct number of atomic particles for vanadium-51 is:
electrons
28
22
23
28
23
(A)
(B)
(C)
(D)
(E)
protons
28
22
28
23
23
neutrons
23
29
23
23
28
Ionization Energies for element X (kJ/mole)
1st
580
2nd
1815
3rd
2740
4th
11600
5th
14800
8. Given the above ionization energies for element “X”, identify this element:
(A) Na
(B) Mg
(C) Al
(D) Si
(E) P
Questions 9-12 refer to atoms for which the occupied orbitals are shown below:
9.
10.
11.
12.
Represents an atom that is chemically unreactive
Represents an atom in an excited state
Represents an atom that has 4 valence electrons
Represents an atom of a transition metal
Part II: Reactions
Write the formulas to show reactants and products. Assume that solutions are aqueous
unless otherwise noted. Represent substances in solutions as ions if the substances are
soluble or ionized in water. Omit formulas for any ions or molecules that are
unchanged by the reactions. (Write net ionic equations for example). Balance the
equations. Answer the question that pertains to each reaction. Total = 10 points.
1. Methane (CH4) burns in air.
a) Balanced equation:
b) Is this reaction exothermic or endothermic?
2. Solid Iron (II) sulfate is formed from its elements under standard conditions.
a) Balanced equation:
b) What is the special name (or symbol) for the enthalpy change of this reaction?
Free Response
Offer a complete answer or solution to each problem or question. Be sure to include all
details of your answer and follow significant digit rules as required.
1. Methanol burns in air according to:
CH3OH (l) + O2 (g)  CO2 (g) + H2O (g)
a) Balance the reaction equation:
b) Use the data provided to determine the Enthalpy of Combustion (Hcomb) for ethanol:
substance
CH3OH (l)
CO2 (g)
H2O (g)
H0f (kJ/mole)
-238.66
-393.51
-241.82
c) If the reaction consumes 2.0 grams of oxygen gas at STP, how much heat will be
released?
2. Explain each of the following:
a) Sodium atoms have a larger atomic radius than Argon atoms.
b) The first ionization energy of Mg is slightly lower than both Na and Al.
c) The electron affinity of Be is very small (basically zero) and the electron affinity of F
is very large.
d) Xenon atoms are very unlikely to gain or lose electrons.
3 The average atomic mass of naturally hydrogen is 1.0079 amu. There are three
common isotopes of naturally occurring hydrogen as indicated in the table below:
Isotope
Protium, H-1
Deuterium, H-2
Tritium, H-3
Mass (amu)
1.0078
2.014
3.016
a) Use the information and the fact that the abundance of tritium is essentially 0% to
determine the percent abundance of protium and deuterium.
b) Determine the number of deuterium atoms that are present in a sample of 1.0 L of
water. Assume the density of water is 1.00 g/ml.
c) A major line in the emission spectrum of hydrogen corresponds to a frequency of
7.32 x 1014 sec-1.
i) Calculate the wavelength, in nanometers, of light that corresponds to this line.
ii) Is the n=5 to n=3 electron transition responsible for this emission line? Justify your
answer with calculations.
d) The ionization energy of hydrogen is 1312 kJ/mole. What wavelength of
electromagnetic radiation would be required to completely ionize a single H atom
according to:
H (g) + (electromagnetic radiation)  H+ (g) + e-
AP Chemistry
Exam #2
Thermochemistry
Atomic Theory
Periodic Properties
Name: _________________________________________________
Answers to part I:
1
2
3
4
5
6
7
8
9
10
11
12