CHEMISTRY 101Name ______
Hour Exam III
December 4, 2008Signature ______
This exam contains 17 questions on 7 numbered pages. Check now to make sure you have a complete exam. You have one hour and fifteen minutes to complete the exam. Determine the best answer to the first 15 questions and enter these on the special answer sheet. Also, circle your responses in this exam booklet. Show all of your work and provide complete answers to questions 16 and 17.
16 (14 pts.)______
17 (16 pts.)______
Total (60 pts)______
CHEMISTRY 101Fall 2008
Hour Exam IIIPage No. 1
1. Which of the following elements has the highest ionization energy?
2.How many of the following are endothermic processes?
I.activated cold pack
II.activated warm pack
III.boiling water on a hot stove
IV.melting ice cube on a kitchen table
3.Which of the following correctly ranks the atoms/ions according to increasing atomic size?
a) Se2– < Br– < Kr < Rb+ < Sr2+
b) Sr2+ < Rb+ < Kr < Br– < Se2–
c) Br– < Se2– < Kr < Rb+ < Sr2+
d) Rb+ < Sr2+ < Se2– < Br– < Kr
e) Kr < Br– < Se2– < Sr2+ < Rb+
4. The atomic model developed by Neils Bohr only works for the hydrogen atom. Choose the best answer that describes why this model does not work for other atoms.
a)Hydrogen is the only element that does actually have orbits around the nucleus. The others have orbitals instead.
b)The hydrogen atom has only one proton. The nuclei of other atoms would be able to pull the electrons out of their orbits.
c)The hydrogen atom has only one electron. Since other elements have more than one electron, the repulsions between electrons cannot be described by this model.
d)Other atoms are larger than hydrogen atoms, so they fill up too much space to be defined by orbits.
e)Hydrogen is the only element that has quantized energy levels like those described by this model.
5. Which of the following is a possible electron configuration for an excited fluoride ion in sodium fluoride?
6.Which of the following supports why Lewis structures are not a completely accurate way to draw molecules?
a) The Lewis structure for O2 shows all electrons as paired but when liquid O2 is poured onto a magnet, it behaves as a molecule with an unpaired electron.
b) We cannot say for certain where an electron is located yet when drawing Lewis structures, we assume the electrons are right where we place them.
c) When adding up the number of valence electrons for a molecule, it is possible to get an odd number which would make it impossible to satisfy the octet rule for all atoms.
d) All of the above statements support why Lewis structures are not a completely accurate way to draw molecules.
e) Lewis structures are the most accurate way to draw molecules and are completely correct.
7. Which of the following is true regarding the atom?
a)All atoms of the same element are identical.
b)Negatively charged particles are embedded in a positively charged cloud throughout the atom.
c)As verified by Rutherford, only positively charged particles called protons are found inside the nucleus.
d)Electrons located further from the nucleus have more predictable behavior because they contain less energy.
e)Electrons display both particle-like behavior (they have mass) and wave-like behavior (they are associated with probability).
Consider the molecule SeO2 for questions 8 and 9.
8.What is the bond angle around the central atom?
9.Which of the following statements are true?
I.The electron geometry of the molecule is trigonal planar.
II.The shape of the molecule is linear.
III.The number of effective pairs around the central atom is four.
IV.The molecule is polar overall.
V.The molecule will exhibit dipole-dipole interactions.
a)I, IV, V
b)I, III, IV, V
c)I, II, III, IV, V
d)I, II, III
10.If it takes energy to remove an electron from an atom, why would an ionic bond occur? Choose the best answer.
a)Each atom wants to have a noble gas configuration so it will absorb that energy in order to make that happen.
b)The final process of the two ions electrostatically bonding together releases a lot more energy than what was required to remove the electron.
c)The protons of atoms attract electrons from neighboring atoms and a sharing of electrons occurs to complete the bond.
d)Bonding does not involve electrons. It involves an exchange of neutrons in the nucleus of each atom.
e)Ionic bonds, especially between metals and nonmetals, do not occur. They are not possible.
Consider the following compounds to answer questions 11 – 13.
ICl3 SeCl6 NF3 CO32–
11.How many of the compounds above do not satisfy the octet rule for each atom?
12. How many of the compounds above are polar overall?
13.How many of the compounds above exhibit London dispersion forces?
14.Consider the following processes where an electron is removed:
I.Ca → Ca+ + e–
II.Ca+ → Ca2+ + e–
III.Ca2+ → Ca3+ + e–
Which process will require the least amount of energy to remove the electron and why? Choose the best answer.
a)Process III. Once the valence electrons are removed, calcium is more stable and more able to give up electrons.
b)Process I. Its effective nuclear charge is not as strong and thus does not “hold” the electrons as tightly.
c)Process II. Calcium wants to be like a noble gas and in fact releases energy when losing the electron to become Ca2+.
d)Process II. Calcium wants to be like a noble gas and although energy is not released, the least amount of energy is required.
e)Process I and Process II will require the same amount of energy since the electrons are removed from the same energy level.
15.Which of the following drawings best represents how we fill orbitals for the ground state of an atom of oxygen, O?
16.In both lecture and lab, you saw many different colors produced by salts in a flame. Answer the questions below as thoroughly as you can. Only complete and coherent explanations will receive full credit. Please limit your answers to the space provided.
a)What was the purpose of adding heat to each salt?
b)Why were there colors at all?
c)Why were the colors different?
d)How would the observations be different if energy levels in the atom were not
17. Examine the following pairs of molecules. Explain which molecule will have the stronger intermolecular forces. In your explanation, include the:
- Lewis structure
- electron geometry
- all intermolecular forces where applicable
- strongest intermolecular force (and how you determined this).
Only complete and coherent explanations will receive full credit. Please limit your answers to the space provided.
a)BF3 and PF3
b)CCl4 and XeCl4
c)N2O and H2O (For N2O, one of the nitrogen atoms is the central atom.)
d)IBr2– and IF5