CHEM 177 – Exam 4 Practice
S22 CB
These questions are representative of the questions you might find on the Canvas exam; you may find the
questions useful as you prepare for the exam in addition to studying, working through the modules, practicing
on homework and end of chatper problems, asking questions to your TA and instructor.
This is not an exact imitation of the exam.
1.
Which one of the following atoms has the largest diameter?
a.
b.
c.
d.
2.
Consider the periodic table. In each row (period) the atoms with the highest first ionization energy are
__________.
a.
b.
c.
d.
e.
3.
-908 kJ/mol
+908 kJ/mol
-1777 kJ/mol
-3477 kJ/mol
Which of the following (anions/atom/cations) has the smallest radius?
S2- Cl- Ar K+ Ca2+
a.
b.
c.
d.
e.
5.
the largest atoms
the alkali metals (group 1)
the alkaline earth metals (group 2)
the halogens (group 17)
the noble gases (group 18)
The lattice energy of sodium fluoride, NaF, is -908 kJ/mol. With the pairs Na+/Ca2+ and F-/O2- having
roughly the same ionic radii, what would you expect the lattice energy of CaO to be?
a.
b.
c.
d.
4.
O
F
S
Cl
S2ClAr
K+
Ca2+
In ethane, C2H6, ethene (ethylene), C2H4, and ethyne (acetylene), C2H2, there are direct carbon-carbon
bonds. Which one is the shortest?
a.
b.
c.
d.
The carbon-carbon bond in ethane is the shortest.
The carbon-carbon bond in ethene is the shortest.
The carbon-carbon bond in ethyne is the shortest.
Carbon-carbon bonds always have the same length.
2
6.
Rank the H-X bonds in HX = HF, HCl, HBr, HI from most polar to least polar (> means “more polar
than”).
a.
b.
c.
d.
7.
According to valence bond theory, which orbitals overlap in the formation of the carbon-carbon sbond and the π-bond in ethene, C2H4?
a.
b.
c.
d.
8.
1
2
3
4
What is the hybridization of the nitrogen atom in the nitrate ion, NO3− ?
a.
b.
c.
d.
10.
σ: 2s and 2s; π: 2p and 2p
σ: one of sp2 and one of sp2; π: another one of sp2 and another one of sp2
σ: one of sp2 and one of sp2; π: 2p and 2p
σ: 2p and 2p; π: one of sp2 and one of sp2
How many reasonable resonance structures does nitric acid, HNO3, have? Obey the octet rule!
a.
b.
c.
d.
9.
HF > HCl > HBr > HI
HBr > HCl > HF > HI
HI > HBr > HCl > HF
H-X bonds always have the same polarity.
sp
sp2
sp3
N is not hybridized
Which one has the smallest bond angle at the central atom?
a.
b.
c.
d.
H2 O
NH3
CH4
They all have the same bond angle
3
11.
Which of the structures A, B or C represents the correct molecular structure of SF4?
(E is meant to represent a generic element, which in this case would be S)
a.
b.
c.
d.
12.
A
B
C
none
Consider the structures A, B, C and match them with their correct name, picking from the choices
below. E represents a generic element.
Linear
Trigonal planar
Tethraedral
Trigonal bipyramidal
Octahedral
Bent
Trigonal pyramidal
Seesaw
T-shaped
Square planar
Square pyramidal
13.
In the Molecular Orbital diagram for the B2 molecule, how many electrons are located in antibonding
orbitals?
a.
b.
c.
d.
0
2
4
6
4
14.
Based on the molecular orbital theory, which of these statements is TRUE? You have to sketch an
orbital diagram for each species to be able to answer and you may wish to refer to the MO diagrams
on FIGURE 9.38 of the text. Also recall the relationship between bond order and bond length.
a. C2+ has a shorter bond length that C2
b. C2+ has an identical bond length as C2
c. C2+ has a longer bond length that C2
15.
Based on the molecular orbital theory, which of these statements is TRUE? You have to sketch an
orbital diagram for each species to be able to answer and you may wish to refer to the MO diagrams
on FIGURE 9.38 of the text.
a. C2+ is diamagnetic
b. C2+ is paramagnetic
c. Dia- or paramagnetism are impossible to determine for C2+