1.
(4 pts) For a given substance which is generally larger, the heat of vaporization or the heat of fusion? Circle
the answer.
a) Heat of vaporization
2.
b) Heat of fusion
(4 pts) Which one of the following has the longest CO bond length? Circle the correct answer.
H2CO
CO
3. (20 pts)
a)
CO32–
CH3OCH3
Circle the formula that best fits each of the following descriptions:
number of σ-bonds in N2F2
1
2
b) hybridization on the central chlorine atom in ClO2–
c)
CO2
most polar bond
C–H
N–H
d) greatest bond energy (as predicted by MO theory)
O2
3
4
5
sp
sp2
sp3
dsp3
O–H
O 2+
O 2–
O22–
e)
greatest electronegativity
K
Si
S
Ar
f)
contains one π-bond
CN–
SO2
NO+
CO2
g) greatest viscosity
CH3 CH2 CH2CH3
h) higher vapor pressure at 1 atm, 25oC
CH3OCH3
d2sp3
CH3CH2CH2OH
CH3CH2OH
HOCH2CH2OH
H 2O
i)
lowest freezing point
H 2O
O2
He
CO2
j)
highest boiling point
BCl3
HCN
NH4Cl
SiH4
1
4.
(8 pts) Indicate the hybridization on the carbon atoms.
O
||
H 3C – C Ł C – C – O – H
1
5.
2
3
4
Hybridization on first carbon:
Hybridization on third carbon:
Hybridization on second carbon:
Hybridization on fourth carbon:
(4 pts) Indicate the approximate bond angles, a, b, c and d.
b
O
H3C – C C – C – O – H
a
6.
c
d
Angle a:
Angle c:
Angle b:
Angle d:
a)
Indicate the hybridization on the carbon atoms and the nitrogen atoms in cyanuric acid (the
molecule shown).
H
(2 pts) Hybridization on carbon:
O
(2 pts) Hybridization on nitrogen:
b) (2 pts)
How many π-bonds are there in cyanuric acid?
c)
How many σ-bonds are there in cyanuric acid?
d) (2 pts)
C
N
H
(2 pts)
N
C
O
N
C
O
H
Are all the atoms in cyanuric acid in the same plane? Circle the answer.
Yes
No
2
7. (6 pts) For each of the following molecules, write the Lewis structure, predict the molecular geometry, and if the
molecule is polar indicate the direction of the dipole. Nitrogen is the central atom in NO2–.
molecular geometry
Lewis structure
a)
polarity
H 3O +
b) NO2–
8.
9.
(9 pts) Indicate the dominant intermolecular force for each of the following substances.
a) SO2
b) SF6
c) HCl
d) LiF
e) CO2
f) SO3
g) C2H6
h) CaCl2
i) CH3OH
(4 pts) A substance does not conduct electricity in liquid or solid form. It is soft and has a low melting point (below
100oC). These properties are characteristic of which one of the following crystalline solids? Circle the correct answer.
a) ionic
b) metallic
c) molecular
d) covalent (atomic network)
10. (6 pts) Indicate the type of crystalline solid formed for each of the following substances.
11.
a) H2S
b) P
c) KBr
d) SiO2
e) Ca
f) Na2O
(6 pts) Draw the Lewis structure for acetate, CH3COO–, including resonance structures.
3
12. a)
(3pts) Consider the phase diagram for water. Label the regions (indicate the phase in region A, B and C).
B
P (atm)
A
•
•C
T (oC)
b) (3 pts) Starting at point A, what phase change occurs if the pressure is increased at constant temperature. Circle the
answer.
Liquid —> Solid
Liquid —> Gas
Solid —> Liquid
Gas —> Solid
Solid —> Gas
Gas —> Liquid
b) (3 pts) Starting at point C, what phase change occurs if the temperature is lowered at constant pressure. Circle the
answer.
Liquid —> Solid
Liquid —> Gas
Solid —> Liquid
Gas —> Solid
Solid —> Gas
Gas —> Liquid
13. (10 pts) As a result of a chemical reaction, 0.132 g of H2O is produced and maintained at a temperature of 50.0oC in a
closed flask of 525-mL volume. For water, ΔHvap = 44 kJ/mol.
Will water be present as liquid only, as vapor only, or as liquid and vapor in equilibrium? SHOW YOUR WORK
NO WORK = NO CREDIT
4