Download Chemistry 215 Quiz 1 (20 points)

Name
Chemistry 111A General Chemistry
Practice Exam 3
M2
3RT u1
Useful equations: PV=nRT, PM=DRT, u 
,

u2
M1
M
Section 1 - Multiple Choice (mark correct answer on Scantron- 2.5 points each)
1.
2.
3.
4.
5.
6.
The electron-domain geometry and the molecular geometry of a molecule of the
general formula ABn will always be the same if
a)
there are no lone pairs on the central atom
b)
there is more than one central atom
c)
n is greater than four
d)
n is less than four
e)
the octet rule is obeyed
A double bond consists of how many pairs of electrons shared between two atoms?
a)
0
b)
1
c)
2
d)
3
e)
4
A valid Lewis structure of which of the following cannot be drawn without violating
the octet rule.
a)
PO43–
b)
SiF4
c)
CF4
d)
SeF4
e)
NF3
To convert from one resonance structure to another
a)
only electrons can be moved
b)
only atoms can be moved
c)
electrons and atoms can both be moved
d)
neither electrons nor atoms can be moved
e)
electrons must be added
The blending of one s atomic orbital and two p atomic orbitals produces
a)
three sp hybrid orbitals
b)
two sp2 hybrid orbitals
c)
three sp3 hybrid orbitals
d)
two sp3 hybrid orbitals
e)
three sp2 hybrid orbitals
Molecular compounds of low molecular weight tend to be gases at room
temperature. Which of the following is most likely not a gas at room temperature?
a)
Cl2
b)
HCl
c)
LiCl
d)
H2
e)
CH4
7.
8.
9.
10.
11.
12.
A gas
a)
b)
c)
d)
e)
is considered "ideal" if
it is not compressible
one mole of it occupies exactly 1 liter at standard temperature and pressure
it can be shown to occupy zero volume at 0C.
its behavior is described by the ideal-gas equation
one mole of it in a one-liter container exerts a pressure of exactly 1 atm at
room temperature
Of the following gases, which will have the greatest rate of effusion at a given
temperature.
a)
NH3
b)
CH4
c)
Ar
d)
HBr
e)
HCl
The principal source of the difference in the normal boiling points of ICl (97C;
molecular mass 162 amu) and Br2 (59C; molecular mass 160 amu) is
a)
London-dispersion forces
b)
dipole-dipole interactions
c)
hydrogen bonding
d)
both hydrogen-bonding and dipole-dipole interactions
e)
both dipole-dipole interactions and London dispersion forces
Large intermolecular forces in a substance are manifested by
a)
low vapor pressure
b)
high boiling point
c)
high heats of fusion and vaporization
d)
high critical temperatures and pressures
e)
all of the above
Cl2 and N2 react according to the following equation
3Cl2(g) + N2(g)  2NCl3(g)
If 4 L of a stoichiometric mixture of chlorine and nitrogen are converted to nitrogen
trichloride under conditions of constant temperature and pressure what is the
volume of NCl3(g) produced?
a)
1L
b)
2L
c)
3L
d)
4L
e)
none of the above
In which of the following molecules is hydrogen bonding likely to be the most
significant component of the total intermolecular forces?
a)
CH4
b)
C5H11OH
c)
C6H13NH2
d)
CH3OH
e)
CO2
13.
14.
15.
16.
Which of the following molecules or ions will exhibit delocalized bonding?
NO2– NH4+ N3–
+
a)
NH4 and N3–
b)
NO2– only
c)
NO2–, NH4+, and N3–
d)
N3– only
e)
NO2– and N3–
The carbon-carbon  bond in ethylene CH2CH2, results from the overlap of
a)
sp3 hybrid orbitals
b)
2s atomic orbitals
c)
sp hybrid orbitals
d)
sp2 hybrid orbitals
e)
2p atomic orbitals
According to MO theory, overlap of two s atomic orbitals produces
a)
one bonding molecular orbital and one hybrid orbital
b)
two bonding molecular orbitals
c)
two bonding molecular orbitals and two antibonding molecular orbitals
d)
two bonding molecular orbitals and one antibonding molecular orbital
e)
one bonding molecular orbital and one antibonding molecular orbital
A molecular orbital can accommodate a maximum of __________ electron(s).
a)
one
b)
two
c)
four
d)
six
e)
twelve
Section 2 Short answers (points as indicated)
(4)
1.
The nitrogen pressure at the Venutian surface is 2050 torr and the atmosphere of
Venus is 3.0 mole% N2. What is the surface pressure on Venus in atm?
(5)
2.
What is the RMS velocity of an ammonia molecule at STP?
(6)
3.
Given the following bond enthalpies in
kJ/mol, what is H for the reaction
CH4 + 2 O2  CO2 + 2 H2O
C–O 358
C=O 799
O–O 146
C–H 413
CO 1072
O=O 495
O–H 463
H–H 436
(6)
4.
Use the Kinetic Molecular Theory of Gases to explain why the pressure in a
container increases when the volume is reduced at fixed temperature.
(6)
5.
Nitrogen and hydrogen react completely at elevated temperature and pressure to
form ammonia
N2 (g) + 3 H2 (g)  2 NH3 (g)
If a mixture of 1.00 mole nitrogen and 1.00 mole of hydrogen is heated to a
temperature of 450 °C in a 20.0 L vessel and react according to the equation above
what is the pressure?
(5)
6.
Explain why heats of vaporization are greater than heats of fusion.
(8)
7.
Draw all possible Lewis dot structures for the NNO molecule that satisfy the octet
rule.
a)
b)
(5)
(15)
8.
9.
Determine formal charges for each structure.
Based on the formal charges, rank the structures from least likely to most
likely.
Draw a Lewis dot structure for the allene molecule CH2CCH2.
a)
How many  and how many  bonds does this molecule have?
b)
What is the hybridization around each carbon atom?
For the following compounds write Lewis dot structures and predict the molecular
geometry using VSEPR. Determine the hybridization on the central atom for each
species and state whether the molecule has a dipole moment.
a)
BeF2
b)
BrF4+
c)
XeF4