Chem 130
Fall 2004
Exam 1a Key
Name: __________________
Scores
Last,
First
1-25 (75 pts) 26 (8 pts)
Student No. ****__ __ __ __*
27 (5 pts)
28 (6 pts)
29 (6 pts)
Total: 100 pts
Letter Grade
Please use scantron for questions 1-25 and write answers on the page for 26-29.
1.) The ground state electronic configuration for oxygen (Atomic number = 8) is
a.) 1s22s22p4
b.) 1s22s22p2
c.) 1s22s42p2
d.) 1s22s23s4
e.) 1s22p22p6
2.) How many valence electrons does oxygen have?
a.) 2
b.) 3
c.) 4
d.) 5
e.) 6
For #3-5, the structure of caffeine is shown below:
O
CH3 N *
O
N
CH3
N*
N
CH3
3.) The type of orbitals involved in the carbon (shown in asterisk) to oxygen bond is
a.) sp2-sp3
b.) p-p
c.) sp2-sp2
d.) a and b
e.) b and c
4.) The type of orbitals involved in the carbon (shown in asterisk) to nitrogen bond is
b.) p-p
c.) sp2-sp2
d.) a and b
e.) b and c
a.) sp2-sp3
5.) The hybridization of the nitrogen atom shown in asterisk is
a.) sp
b.) sp2
c.) sp3
d.) p
e.) b and c
6.) Which of the following is correct considering the bond energy of the covalent bonds
shown below?
a.) Csp-Csp>Csp2-Csp2
b.) Csp3-Csp3>Csp2-Csp2
c.) Csp2-Csp2>Csp-Csp
3
2
3
3
d.) Csp -Csp >Csp-Csp
e.) Csp -Csp >Csp-Csp
7.) Considering the bond length of the following covalent bonds, which is not correct?
a.) Csp3-Csp3>Csp-Csp
b.) Csp2-Csp2>Csp-Csp
c.) Csp3-Csp2>Csp-Csp
3
3
2
2
2
2
e.) Csp-Csp>Csp -Csp
d.) Csp -Csp >Csp -Csp
8.) All of the following will have a polar covalent bond except
a.) H2O
b.) CCl4
c.) CH3OH
d.) N2
e.) HCl
9.) The C=C-H bond angle is about
a.) 120o
b.) 180o
c.) 109.5o
d.) 90o
e.) <109.5 o
10.) The geometry of an sp3 hybridized carbon atom is
a.) planar b.) bent c.) trigonal planar d.) trigonal pyramidal e.) tetrahedral
11.) Which of the following contains the most polar bond?
a.) H2O
b.) HCl
c.) HBr
e.) NH3
d.) HF
12.) The more favored conformation for ethane is
a.) flat
b.) eclipsed
c.) staggered
d.) bent
e.) chair
13.) The more favored conformation for cyclohexane is
a.) flat
b.) eclipsed
c.) staggered
d.) bent
e.) chair
14.) Alkanes and cycloalkanes exhibit the following properties except
a.) miscibility with water
b.) chemically inert
c.) being nonpolar
d.) undergo combustion reaction
e.) can be burnt in air
15.) CH3(CH2)6CH3 is
a.) pentane
b.) hexane
c.) heptane
d.) octane
e.) nonane
16.) The carbon with the asterisk shown below is
O
*
a.) primary
b.) secondary
c.) tertiary
d.) quaternary
17.) Combustion of alkanes and cycloalkanes is a reaction of the hydrocarbon with
a.) water
b.) carbon monoxide
c.) carbon dioxide
d.) oxygen
18.) Which of the following is an isopropyl substituent?
CH3
a.) -CH2CH3
b.)-(CH2)2CH3
c.) -CHCH3
CH3
19.) Electronegative elements such as chlorine and oxygen
a.) donate electrons
b.) withdraw electrons
d.) -CCH3
CH3
20.) Given the pKa values: picric acid = 0.38; formic acid = 3.75; phenol = 10; water =
15.7. Which acid has the weakest conjugate base?
a.) phenol
b.) formic acid
c.) picric acid
d.) water
21.) Which of the following compounds has the highest boiling point?
a.) pentane
b.) propane
c.) hexane
d.) butane
e.) heptane
22.) Which of the following structures shows the correct bond polarity?
δ−
CH3
δ+
O
a
δ−
H
δ+
δ−
CH3
O
b
δ+
H
δ−
CH3
δ−
O
c
δ+
H
δ+
δ−
CH3
O
H
d
For #23-25, consider the following information below.
pKa values: Ammonia = 36; acetic acid = 4.76; ammonium ion = 9.24.
O
O
_
?
+
CH3CO
+ NH4
CH3COH + NH3
acetic acid
ammonia
acetate
ammonium
ion
23.) The strongest Bronsted-Lowry acid in the above equation is
a.) acetate
b.) ammonium ion
c.) acetic acid
d.) ammonia
+
24.) The conjugate base of NH4 is
a.) acetate
b.) ammonium ion
c.) acetic acid
25.) The equilibrium for this reaction
a.) favors the products
b.) favors the reactants
26.) Draw correct structures for 4 isomers of C5H10. (8 pts)
d.) ammonia
c.) cannot be predicted
27.) Draw the orbital overlap diagram of the two carbon atoms in acetylene, H-C C-H.
Label all the types of bonds (σ and π) involved in the C-C and C-H bonding. (5 pts)
π
σ
σ
σ
π
28.) Name the following molecules. (6 pts)
CH3
a.)
b.)
CHCH3
CH3
cis-1-isopropyl-3-methylcyclopentane
_______________________________
3-ethyl-5-methyloctane
___________________________
29.) Draw the structures of the following molecules. (6 pts)
a.) Chair conformation of trans-1-ethyl-4-methylcyclohexane
CH2CH3
CH3
2 equatorial positions
b.) Newman projection for eclipsed ethane
HH
H
H
H
H