Chem 1721/1821
Name ________________________________________
Quiz 1
January 31, 2013
ln !!"# = 1.
!!!!"#
!
!
!
+C
R = 8.314 !
q = msΔT
!∙!"#
a.
How many sp3-hybridized atoms are there in this structure? _________
b.
What is the hybridization of the S atom?
c.
What is the approximate C-S-C bond angle (indicated as 1 on the
_________
_________
H
e.
Which orbitals overlap to form the N-H bond (indicated as 2 on the structure)?
!
!
!!
− !
!!
A bond angle of 90° is consistent with both sp and sp d hybridization.
c.
The number of regions of e
−
b.
C
H
H
C
N
C
N
C
H
CH3
N
H
2
_______________
density around an sp3 hybridized atom is the same as the number of regions of e− _______________
Consider a molecule with chemical formula AB3 and a dipole moment ≠ 0. The molecular geometry of this
_______________
Identify (by circling) the compounds in the following list that can hydrogen-bond:
H2
PH3
CH3OH (C is the central atom)
methyl amine, H3C-NH2
Identify (by circling) the compounds in the following list that have London dispersion forces as their primary
intermolcular force:
PCl5
a.
1
S
H
H
_______________
density around an sp3d2 hybridized atom.
a.
H
H
_______ on N with _______ on H
3
b.
b.
H2
PH3
CH3OH
BF3
Consider benzene (C6H6, µ = 0) and 3-pentanone (C2H5C(O)C2H5, µ = 2.7 D). Which has stronger dipole-dipole
forces?
________________________
Which of these {benzene or 3-pentanone} should have the higher boiling point?
________________________
Consider 2 substances A and B. If B has stronger intermolecular forces which one of the following is true?
bp A > bp B
6.
∆!!"#
H
Indicate whether each of the following statements is true or false:
a. The extent of orbital overlap in a π bond is greater than the overlap in a σ bond.
2
C
C
C
What is the total number of π bonds in this structure?
SiH4
5.
= H
C
N
H
compound could be T-shaped.
4.
!!
H
_________
d.
d.
3.
!! Cimetidine is the active ingredient in the over-the-counter medication Tagmet. Consider the structure of this compound
(shown below) to answer the following questions. Note: lone pairs of electrons have been omitted for clarity; all atoms
(except H) obey the octet rule.
structure)?
2.
ln
viscosity B > viscosity A
Pvap B > Pvap A
ΔH°fus B > ΔH°vap B
The normal boiling point of hexane is 342 K. Determine the vapor pressure of hexane (in mmHg) at 298 K. For hexane
ΔH°vap = 31.5 kJ/mol.
7.
Consider the phase diagram shown to the right to answer the following questions.
13.0
a. Give the approximate melting point of this substance at P = 13.0 atm. ___________
b. Which region of the phase diagram {B, C, or D} corresponds to this
substance in its liquid state?
C
G
B
X4
X3
E
5.0
___________
c. Which point {A, E, F, or G} corresponds to a P and T where the liquid and
gas phases coexis in dynamic equilibrium?
X1
9.0
A
1.0
X2
F
D
___________
d. Consider a change that starts at the point labeled X3 and ends at the point X1.
50
100
T, K
200
This change requires a(n) ______________________ {increase, decrease, or no change}
in pressure and a(n) _______________________ {increase, decrease, or no change} in temperature.
8.
Consider 2 substances Q (normal bp = 125°C) and R (normal bp = 80°C).
a. Is the vapor pressure of Q at 25°C less than, greater than or equal to Pvap of Q at 50°C? ______________________
b.
If atmospheric pressure = 750 Torr, is the bp of Q less than, greater than or equal to 125°C? __________________
C3H6O (l) C3H6O (s)
9.
Is the following change endothermic or exothermic?
______________________
10.
For acetone (C3H6O, molar mass = 58.08 g/mol), mp = −95.2°C, bp = 56.4°C, specific heat (liq) = 2.15 J/g°C, and
ΔH°vap = 29.1 kJ/mol. Calculate the total quantity of energy (in kJ) required to convert 125 g C3H6O liquid at 50.0°C to
vapor at 82.5°C.
250
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