CHM 112
Chapter 11 Worksheet: Intermolecular forces
Name ___________________
Q1. If the vapor pressure of Ethylene glycol is 7.23 mm Hg at 95.1˚C and 755 mm Hg at 197.1 ˚C, calculate the heat of
vaporization of ethylene glycol.
65.6 kJ or 65600 J
Q2. Graph the following data for vapor pressure of ammonia using excel or another computer program and from the graph
determine the heat of vaporization and the normal boiling point for NH3.
Temperature in Kelvins
200
210
220
230
235
Q3.
Vapor Pressure (Torr)
65.3
134.3
255.7
456.0
597.0
ΔHvap = 24.7 kJ or 24700 J
Normal boiling point = 239 K or -33.5°C
The heat of vaporization of water is 40.7 kJ/mol. What is the vapor pressure of water at 351 K?
0.439 atm or 334 torr
Q4.
Draw the Lewis Structure for each molecule. Identify the type of intermolecular forces in each species.
Circle the member of the pair with the corresponding property.
(A) Highest boiling point:
CCl4
or
CBr4
(B) Highest vapor pressure:
CH3OH
or
(C) Lowest Viscosity:
(CH 3 ) 2 NH
or
(CH3)3N
(D) Largest ΔH v a p :
LiCl
or
HF
CH3Cl
Q5.
How much heat would be released during the condensation of 5.00 g of Acetone (C3H6O)? The molar heat of vaporization
for acetone is 30.3 kJ/mol.
-2.61 kJ released
Q6.
How much heat is released when 10.0 g of Steam (water vapor) at 100.0 ˚C is cooled to 37.0 ˚C? How much heat is released
when 10.0 g of water at 100.0 ˚C is cooled to 37˚C?
Cooling steam: -25.2 kJ or -25200 J
Cooling water: -2.63 kJ or -2630 J
Does this justify the fact the steam causes more severe burns than water even though they are at the same temperature?
Q7.
List the following molecules in order if increasing boiling points (from low to high boiling point).
a) KBr, CH3CH2CH2CH2CH3, CH2CH2OH
CH3CH2CH2CH2CH3, CH2CH2OH, KBr
b) CH3CH2NH2, CH3CH2-O-CH2CH3, HOCH2CH2CH2CH2OH
Q8. The following molecules have the same molecular formula (C3H8O), yet they have different normal boiling points, as shown.
Explain the difference in the boiling points
Q9.
CO2 forms a solid that sublimes at -78˚C at atmospheric pressure but NO2 forms a liquid that boils at 21˚C at
atmospheric pressure. How does this information support that statement that CO2 is linear molecule but NO2 is a nonlinear molecule?
Q10.
Look at the phase diagram of water below.
What phase changes occur in each of the following cases?
a)
Water at -20.0 ˚C and 21.5 torr is heated to 50 ˚C at a constant
pressure
Melting (and maybe boiling also)
b)
Water at 0 ˚C originally is compressed from a pressure of 2.15
torr to 800 torr at 0 ˚C ?
Melting
Q11.
Q12.
Indicate the type of crystal (molecular, metallic, ionic, or covalent-network) would each of the following compounds
form on solidification. Would each have a high or low melting point?
a) CaCO3
b) Pt
c) ZrO2
d) Kr
e) benzene
f) I2
Ionic
Metallic
Ionic
Atomic
(noble gas)
Molecular
Molecular
Which of the following molecules will have the higher viscosity and why?
Q13.
What intermolecular forces are responsible for the following differences?
a) Xe is a liquid at atmospheric pressure and 120 K while Ar is a gas under the same conditions.
Dispersion (though more dispersion for Xe, because it’s bigger)
b) CH3OH boils at 65 °C while CH3SH boils at 6 °C.
c) H2O has a much higher boiling point than H2S
H-bonding
dispersion, maybe weak dipole-dipole
d) CO2 is a gas at atmospheric pressure and room temperature while CS2 is a liquid.
Q14.
Give an example of each kind of solid and state how the solid is bonded and the consequential relative melting point.
Molecular
Ionic
Atomic (noble
gas)
Example
ice
Kr
Bonding?
H-bonding
Dispersion
low
low
Relative
Melting Point
Atomic
(Metallic)
Network
Covalent
Q15. Sketch the phase diagram for oxygen using the following data:
Triple point, 54.3 K and 1.14 torr; critical point, 154.6 K and 37828 torr; normal melting point, -218.4 °C; and normal
boiling point, -182.9 °C. Does solid oxygen melt under an applied Pressure (like water does)?
(try to sketch the diagram on your own)
Solid oxygen will not melt under applied pressure.