Download Practice Examination 1 - College Chemistry II | CHEM 155 and more Exams Chemistry in PDF only on Docsity!
Exam 1 Heldt
Name: ________________________________ Date_____________
Part I: Show all work in solving each of the problems.
1. For each of the molecules listed below give the total number of electrons, the
complete Lewis Dot structure, the formal charge for each of the atoms in the
molecule, the EPG (electron pair geometry), the shape of the molecule, the polarity
of the molecule, the direction of the dipole moment, the hydridization for the
underlined atoms, and label the bonds. (36 pts)
a. NBr 3
Lewis Structure Total val. electrons________
Show direction of dipole with arrow Formal charge for:
Label bonds as sigma or pi N_______
Br _______
EPG ___________________
Shape __________________
Polarity _________________
Hybridization on N________
Bond Angles _____________
Exam 1 Heldt
b. IOF 3
Lewis Structure Total val. electrons________
Show direction of dipole with arrow Formal charge for:
Label bonds as sigma or pi I _______
O _______
F _______
EPG ___________________
Shape __________________
Polarity _________________
Hybridization on I _______
Bond Angels_____________
c. NO 3
Lewis Structure Total val. electrons________
Show direction of dipole with arrow Formal charge for:
Label bonds as sigma or pi N _______
O _______
O _______
O _______
EPG __________
Shape __________________
Polarity _________________
Hybridization on N________
Bond Angles_____________
Exam 1 Heldt
4. For the following diatomic molecules, Chose the correct energy level and fill in the
electrons correctly in the table below (12 pts)
a. BeH
Molecule:
Total number of electrons
Average atomic number
σ 2 p ***** _____ _____
π 2 p ***** _____ _____ _____ _____
σ 2 p _____ _____
Energy π 2 p _____ _____ _____ _____
σ 2 s * _____ _____
σ 2 s _____ _____
σ 1 s * _____ _____
σ 1 s _____ _____
magnetism
Bond order
Molecule:
Total number of electrons
Average atomic number
σ 2 p ***** _____ _____
π 2 p ***** _____ _____ _____ _____
π 2 p _____ _____ _____ _____
Energy σ 2 p _____ _____
σ 2 s * _____ _____
σ 2 s _____ _____
σ 1 s * _____ _____
σ 1 s _____ _____
magnetism
Bond order
Now write out the molecular orbital electron configuration for: (3 pts)
b. BeH
c. O 2
d. CF
Exam 1 Heldt
Part II. Multiple Choice (25 pts)
- _____In which of he following molecules would you expect the carbon-to-carbon
bond to be the shortest?
a. H 2 C=CH 2 b. H 3 C-CH 3 c. HC≡CH d. all are the same
_____ What are the formal charges on nitrogen and oxygen in the molecule:
a. N is + 5 and O is +
b. N is + 1 and O is 0
c. N is -1 and O is +
d. N is 0 and O is -
- _____ How many lone pairs on sulfur should be shown in the Lewis structure for
hydrogen sulfide (H 2 S)?
a. 0 b. 1 c. 2 d. 3 e. 4
- _____ Which of the following atoms would be the least likely to form an expanded
octet?
a. P b. S c. Cl d. Be e. Br
- _____What is the formal charge on P in PO 4
a. 0 b. +1 c. +2 d. -1 e. -
- _____ After drawing the Lewis dot structure of NO 2 -
, pick the incorrect statement of
the following.
a. One N-O bond is a double bond.
b. There are no lone pairs on N.
c. The molecule exhibits resonance.
d. The formal charge on one of the oxygen atoms is –
e. The formal charge on nitrogen is 0
- _____ Which of the following species central atom (underlined) has sp hybridization?
a. CCl 4
b. PF 6
c. NH 3 d. SO 2
e. BeH 2
- _____ Which of the following has a molecular structure best described as involving
an "incomplete octet"?
a. CH 4 b. NH 3 c. H 2 O d. BeF 2 e. NaCl
- _____ Which of the following is a linear molecules?
a. CH 4 b. NH 3 c. H 2 O d. BeF 2 e. none of these
- _____ Which of the following species has a trigonal pyramidal shape?
a. CH 4 b. NH 3 c. H 2 O d. BeF 2 e. NaCl
.. ..
:N=O=N:
Exam 1 Heldt
- _____ Hydroazidic acid (HN 3 ) has five covalent bonds. Which of the following
structures does not illustrate a correct arrangement of bonds in HN 3?
a. H-N≡N-N
b. H=N-N=N
c. H-N≡N-N
d. H-N=N=N
- _____Rank the following molecular geometries is order of increasing bond angle.
a. Linear < Trigonal planar < Tetrahedral
b. Linear < Tetrahedral < Trigonal planar
c. Trigonal planar < Tetrahedral < Linear
d. Tetrahedral < Linear < Trigonal planar
e. Tetrahedral < Trigonal planar < Linear
- _____The concept of an anti-bonding orbital is unique to the
a. theory of bond hybridization
b. valence bond theory
c. molecular orbital theory
d. concept of resonance
e. electrostatic repulsion theory
- _____ Give the total number of valence electrons in the molecule BF 3
a. 20 b. 21 c. 22 d. 23 e. 24
- _____How does the hybridization of the sulfur atoms change in the series SF 2
, SF
4
SF 6?
a. sp
3
, sp
3
d, sp
3
d
2
b. sp, sp
3
, sp
3
d
2
c. sp, sp
3
d, sp
3
d
2
d. sp
3 , sp
3 , sp
3 d
2
e. sp
3 , sp
3 d
2 , sp
3 d
2
- _____ A double bond that results from the sharing of four electrons consists of:
a. 2 sigma bonds
b. one sigma and one pi bond
c. one sigma bond
d. two pi bonds
e. none of these
