Department of
Chemistry, Geosciences, and Environmental Science
Chemistry
1054-010 College
Chemistry Summer I
2005
Exam 3
Name:_______________________________________________________
(Please write your name legibly)
Read all directions and questions carefully!! This exam consists of two parts. The first part consists of 10 multiple choice questions worth four points each for a total of 40 points. The second part consists of five numerical problems worth either 10 or 15 points per question for a total of 60 points. Show all your work necessary for the numerical problems as partial credit will be given for those problems.
Possibly Useful Constants and Equations
Planck's Law: 
Speed of light: c
= 2.998 × 108 m/s
deBroglie wavelength: 
Rydberg formula:
Score
Part 1 (40 points):_____________________
Part 2 (60 points):_____________________
Total (100 points):_____________________
Don’t forget to put your
name on this test!
Good Luck!!
Part 1
Multiple Choice
Please indicate the answer to each question by putting your choice in the space provided. There is only one correct answer for each question. There will be 10 multiple choice questions worth 4 points each.
1. The wavelength of light that has a frequency of 1.20 × 1013 Hz is _____________________ m.
(a) 25.0 (c) 0.0400
(b) 12.0 (d) 2.50 × 10-5
(e) 2.5
Answer: D 
2. Pictures of orbitals, such as the ones shown above, represent:
(a) the surface on which the electron travels about the atom.
(b) the region in which the electron can definitely be found.
(c) the region in which the electron is likely to be found.
Answer: C
3. What is the l number associated with the orbitals pictured above?
(a) –1 (c) 1
(b) 0 (d) 2
(e) 3
Answer: D
4. Which one of the following has the smallest radius based solely on their positions in the periodic table?
(a) Na (c) P
(b) Cl (d) Br
(e) Mg
Answer: B
5. Which of the following ions has the largest ionic radius?
(a) O2- (c) Na+
(b) F¯ (d) Mg2+
(e) Al3+
Answer: A
6. Which of the following properties is not characteristic of metals?
(a) acidic oxides (c) malleable
(b) low ionization energies (d) ductile
(e) These are all metallic properties
Answer: A
7. In nature, the noble gases exist as:
(a) gaseous fluoride compounds (c) solids in rocks and minerals
(b) alkali metal salts (d) monatomic gases
(e) acidic oxide compounds
Answer: D
8. Based on the octet rule, phosphorus most likely forms a _______________ ion.
(a) P3+ (c) P5+
(b) P3- (d) P5-
(e) P+
Answer: B
9. The only noble gas without 8 valence electrons is:
(a) Ar (c) He
(b) Ne (d) Kr
(e) All the noble gases have 8 valence electrons
Answer: C
10. Which of the following atoms has the highest electronegativity?
(a) O (c) S
(b) N (d) P
(e) Se
Answer: A
Part 2
Numerical Problems
Solve the following problems, keeping track of significant figures where applicable. Please show all the work necessary to obtain your answer in order to receive partial credit for possibly wrong answers. Generally, full credit will not be given for the correct answer without any of the work performed to obtain the answer being shown on the paper. Each question is worth either 10 or 15 points.
11. (10 points) Write the ground state electron configuration for the following atoms or ions. You may use the shorthand notation if you wish.
(a) Ga: 31 electrons: 1s22s22p23s23p64s23d104p1 or [Ar]4s23d104p1
(b) Sc 21 electrons: 1s22s22p23s23p64s23d1 or [Ar]4s23d1
(c) P¯ 16 electrons: 1s22s22p63s23p4 or [Ne]3s23p4
(d) Mn2+ 23
electrons: 1s22s22p63s23p63d5
or [Ar]3s23p63d
(e) Cu 29 electrons: 1s22s22p63s23p64s13d10 or [Ar]4s13d10
12. (15 points) Write the most correct Lewis structure for the following molecules or ions:
(a) NH3 8 valence electrons (b) CO32- 24 valence electrons
(c) BeF2 16 valence electrons (d) H2SO4 32 valence electrons
less than an octet greater
than an octet
(e) CCl4 
13. (10 points) Calculate the wavelength, in centimeters, of microwave radiation of frequency equal to 2.25 × 1010 Hz. What is the energy of one photon of this radiation?
Calculate the wavelength from the frequency:
Calculate the energy using Planck’s Law:
14. (10 points) Predict the products when the following reactants are mixed. Balance the chemical equation for the particular reaction.
(a) Mg(s) + N2(g) ¾¾® ??
Group
charges for: Mg-2+, N-3–
Formula
of salt formed from Mg2+ and N3- is Mg3N2.
The balanced reaction is:
3 Mg(s) + N2(g) ¾¾® Mg3N2(s)
(b) K(s) + H2O(l) ¾¾® ??
Reaction
of alkali metal with water:
2 K(s) + 2 H2O(l) ¾¾® 2 KOH(aq) + H2(g)
(c) Na(s) + O2(g) ¾¾® ??
Reaction
of sodium with oxygen produces sodium peroxide:
2 Na(s) + O2(g) ¾¾® Na2O2(s)
(d) Ca(s) + S8(s) ¾¾® ??
Group
charges: Ca-2+, S-2–
Formula
of salt formed from Ca2+ and S2- is CaS. The
balanced reaction is:
8 Ca(s) + S8(s) ¾¾® 8 CaS(s)
15. (15 points) Use the table of average bond enthalpies below to estimate the DH for the following gas phase reaction:
See table 8.5 on page 330 for bond enthalpies. Breaking the bonds in the reactants will require the following energies:
Forming the bonds in the products will release this much energy:
DH is equal to:
DH = 1483 kJ – 1587 kJ = –104 kJ
10 points extra credit Please give the complete definition for 2 out of following three terms. You will be given 5 points for each definition. Only answer 2 out of the three, if you answer all 3 only the first two will be graded. No credit will be given for incomplete definitions.
Electronegativity: the ability of an atom to attract shared
pairs of electrons to itself
Paramagnetic: any species with unpaired electrons
Ionization Energy:
the energy required to remove an electron from a gaseous atom or ion.