Houston Community College System
Chemistry 1411, Fall 2010
EXAM # 3
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CHEM 1411 EXAM # 3
(Chapters 7, 8, 9, 10)
Name:______________________________
Score:
Directions- please answer the following multiple-choice questions next to each number. Please show all your work for
bonus question and part(2) questions in the space provided.
Part (1) - Multiple Choice - (3 points each)
_____ 1. How many unpaired electrons are in the Lewis dot symbol of a phosphorus atom?
A.7
B. 3
C. 5
D. 1
E.8
_____ 2. Which of the following molecules/ions is nonpolar?
A. CH4
C. CN-
B. O2
D. A and B
E. A and C
_____ 3. Determine the total number of sigma and pi bonds in the following molecular structure.
H
H
O
C
C
C
H
C
H
C
C
C
C
C
A. 11 , 6 
B. 11 , 11 
H
C. 16 , 6 
H
D. 16 , 11 
E. none of these
_____ 4. Which of the following molecules has highest number of valence electrons?
A. CaO
B. NaBr
C. AlCl3
D. SO4
E. CO2
_____ 5. Identify the molecule that has 8 bonding electons
A. CO2
B. HCl
C. H2O
D. SO2
E. all of these
_____ 6. How many non-bonding electrons are present in PH3 molecule?
A. 2
B. 6
C. 4
D. 5
E. 10
_____ 7. Identify the molecule that has linear geometry
A. SO2
B. O3
C. CO2
D. SeO2
E. None of them
_____ 8. The configuration (σ1s)2(σ*1s)2 (σ2s)2(σ*2s)2 (π2p)2(π2p)2(σ2p)2 is the molecular orbital description for the
ground state of
A. Li2
B. B2
C. Be2
2
D. B22+
E. C22-
_____ 9. What is the bond order of CN- ion?
A. 1
B. 2
C. 3
D. 1.5
E. 2.5
_____ 10. What is the hybridization of carbon in Ethen, H2C=CH2
A. SP3
B. sp2
D. sp3d
C. sp
E. sp3d2
_____11. What is the electron arrangement and molecular geometry in H2CO?
A. Tetrahedron and Tetrahedron
B. Tetrahedron and Trigonal planar
C. Trigonal planar and trigonal planar
D. Linear and linear
E. Tetrahedron and Linear
____ 12. Which of the following molecules is paramagnetic?
i. C2
ii. H2
A. all of them
iii. N2
iv. O2
B. i
C. ii
D. i iv
E. iii
_____ 13. Identify the compound that has dispersion forces as dominant intermolecular forces.
A. H2O
B. CH4
C. Cl2
D. A and B
E. B and C
_____ 14. What are the hybridization and the approximate bond angle CH4?
A. sp2, 104o
B. sp3, 109.5o
C. sp, 180o
D. sp3d, 900
E. sp3d2, 180o
_____ 15. The electron-pair geometry and molecular geometry of BH4- are respectively
A. Tetrahedral, tetrahedral
C. tetrahedral, trigonal pyramid
E. octahedral, square planar
B. tetrahedral, trigonal planar
D. trigonal bipyramidal, trigonal pyramidal
_____ 16. Which of the following molecules has dipole-dipole intermolecular force?
A. H2O
B. H-F
C. H-Cl
D. NH3
NaCl
_____ 16. Which of the following has bond order of 2?
I. F2-2
A. I & III
II. NO-
B. I & IV
III) O2
IV) N2
C. I only
D. III Only
E. II & III
_____ 17. Which of the following crystal will be assigned 2 particles?
A. SCC
B. BCC
C. FCC
D. All of them
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E. None of them
_____ 18. Which of the following atoms cannot accommodate an excess of 8 electrons in Lewis structures where
they are the central atom?
A. Xe
B. Cl
C. Si
D. F
E. all of them
_____ 19. How many atoms/ions/molecules are assigned to Face centered cube
A. 4
B. 2
C. 3
D. 1
E. 6
_____20. Choose from the molecules listed below, the one with the weakest intermolecular force
A.
H2O
B. H-F
C. H-Cl
Part (2) - Show all your work. ( 8 points each)
21. a. Draw molecular orbital configuration of N2
b. Bond order
c. magnetic property
22. Draw Lewis dot (electron) structure for SF6 and determine
a) electron geometry
b) molecular geometry
23. Use Molecular orbital theory to predict the following for NO- :
a) Its molecular orbital configuration
b) Its bond order
c) Is it paramagnetic or diamagnetic?
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D. Cl2
E. NH3
24. Draw the dot structure of Cl2CO and write the formal charges of all the atoms
25. Draw all the resonance structures of the nitrate ion, NO3-
26. Consider the following three resonance structures of the thiosulfate ion, S2O3-2.
a. Assign formal charges to all atoms in all three structures
b. Pick the major structure based on the formal charges. S is less electronegative than O.
..
..
:O:
:O:
:O-S-S:
..
:O:
:O=S=S:
:O=S-S:
..
:O:
..
Structure I
..
:O:
:O:
..
..
Structure II
Structure III
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