CH Bocknack 310M Spring 2010 Graded HW#02 Assignment Handout
Submission Deadline: 5:00 p.m., Tuesday, 2/2/10 Your answers to these multiple choice questions must be submitted online, using Blackboard! Please use the Graded HW#02 Submission Form, which you will find inside the Graded Homework Assignment #02 folder. Previously submitted answers can be changed at any time up until the submission deadline! All answers must be submitted online before the submission deadline LATE SUBMISSION OF HOMEWORK IS NOT POSSIBLE, FOR ANY REASON!!! This assignment is worth a total of 40 raw points. To answer Questions 1 through 3, you will probably find it helpful to draw a Lewis structure for the molecular formula
CCl3.
[Cl stands for the element chlorine.]
1. (2 points) W hat is the total number of valence electrons that should be shown explicitly as bonding pairs and/or lone pairs in the correct Lewis structure for CCl3 ? A. 22 B. 23 C. 24 D. 25 E. 26
2. (4 points) What is the geometrical arrangement of electron groups surrounding the central carbon atom in the correct Lewis structure for CCl3 ? A. Trigonal planar B. Tetrahedral C. Linear
3. (4 points) Is the CCl3 molecule polar or nonpolar? The molecule is nonpolar if the net molecular dipole moment is zero. The molecule is polar if the net molecular dipole moment is not zero. A. Polar molecule B. Nonpolar molecule
To answer Questions 4 through 6, you will probably find it helpful to draw a Lewis structure for the condensed structural formula bonding connectivity.
(CH3)2CO.
Remember, a condensed structural formula suggests the
4. (2 points) W hat is the total number of valence electrons that should be shown explicitly as bonding pairs and/or lone pairs in the correct Lewis structure for (CH3)2CO? A. 22 B. 23 C. 24 D. 25 E. 26
5. (4 points) What is the geometrical arrangement of electron groups surrounding the carbon atom that is bonded directly to oxygen in the correct Lewis structure for (CH3)2CO? A. Trigonal planar B. Tetrahedral C. Linear
6. (4 points) Is the (CH3)2CO molecule polar or nonpolar? The molecule is nonpolar if the net molecular dipole moment is zero. The molecule is polar the if net molecular dipole moment is not zero. A. Polar molecule B. Nonpolar molecule
Questions 7 and 8 refer to the Lewis structure shown below. All valence electrons are shown explicitly in this structure, so you dont need to worry about adding lone pairs or bonds. Nonzero formal charges are not shown explicitly, however.
H
7
7. (4 points) W hat is the formal charge on the nitrogen atom marked 7 in the structure on the left? A. 2 B. 1 C. 0 D. +1 E. +2
HNH H O H C H C H C O
8. (4 points) W hat is the overall charge on the molecule shown at the left? A. 2 B. 1 C. 0 D. +1 E. +2
Questions 9 and 10 refer to the resonance structures shown below. All valence electrons are shown explicitly in each resonance structure, so you dont need to worry about adding lone pairs or bonds. Nonzero formal charges are not shown explicitly, however. 9. (4 points) Which resonance structure(s) to the left have a formal charge of zero on the nitrogen atom that is bonded directly to carbon? Pick one choice from the menu below that best answers this question! A. B. I only II only C. D. III only I and II E. F. I and III II and III G. H. I, II, and III None of them
I
H3C
N
N
N
II
H3C
N
N
N
10. (4 points) Which resonance structure(s) to the left are LEAST IMPORTANT in their overall contribution to the true structure of the resonance hybrid. Pick one choice from the menu below that best answers this question! A. I only II only III only D. E. F. G. I and II are of equal importance and are less important than III. I and III are of equal importance and are less important than II. II and III are of equal importance and are less important than I. All structures are of equal importance.
III
H3C
N
N
N
B. C.
11. (4 points) In which choice are the nonequivalent resonance structures shown below ranked correctly according to INCREASING importance? In other words, the LEAST IMPORTANT resonance structure is listed FIRST, and the MOST IMPORTANT resonance structure is listed LAST.
O
O
O
A. B. I < II < III I < III < II C. D. II < I < III II < III < I E. F. III < I < II III < II < I
N
H
N
H
N
H
I
II
III 2