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Chapter 11 – Exam-Type Questions
Multiple Choice
- Acetaldehyde (pictured to the right) is a product of the oxidation of ethanol in your
liver, and is the molecule primarily responsible for hangovers. Which one of the
following statements best describes the intermolecular forces experienced by a
molecule of acetaldehyde in its pure liquid form and when it is dissolved in water.
a. Acetaldehyde is a nonpolar molecule, so it is attracted to other molecules of
acetaldehyde in the pure liquid or to water only via dispersion forces.
b. Acetaldehyde molecules are attracted to other molecules of acetaldehyde (in the
pure liquid) and water via dispersion and dipolar forces. Since acetaldehyde does
not contain any O–H bonds, it cannot form hydrogen bonds with other acetaldehyde
molecules or with water molecules.
c. Acetaldehyde molecules are attracted to other molecules of acetaldehyde (in the
pure liquid) and water via dispersion, dipolar forces, and hydrogen bonds. Since
acetaldehyde does not contain any O–H bonds, it cannot form hydrogen bonds with
other acetaldehyde molecules or with water molecules.
d. Acetaldehyde molecules are attracted to other molecules of acetaldehyde (in the
pure liquid) and water via dipolar forces. Dispersion forces are not present. Since
acetaldehyde does not contain any O–H bonds, it cannot form hydrogen bonds with
other acetaldehyde molecules or with water molecules.
e. In its pure liquid form, acetaldehyde molecules are attracted to each other via
dispersion and dipolar forces. When dissolved in water, acetaldehyde molecules can
form hydrogen bonds between the O lone pairs of acetaldehyde and the H atoms of
water molecules; acetaldehyde and water molecules are also attracted to each other
via dispersion and dipolar forces.
- An unknown solid material is crystalline and has a face-centred cubic unit cell. The
material has a band gap of zero and is a conductor of electricity, with conductivity
decreasing as temperature increases. The unknown material is most likely which one of
the following types of solids?
a. Ceramic
b. Ionic
c. Metal
d. Metalloid
e. Network covalent
H
O
- Why does a meniscus form when you fill a glass pipette or burette with an aqueous
solution?
a. The adhesive forces between glass and water are stronger than the cohesive forces
between water molecules in the liquid, allowing the liquid to rise up the sides of the
glass against the force of gravity.
b. The anions in the solution are attracted to the silicate cations in the glass, allowing
the liquid to rise up the sides of the glass against the force of gravity.
c. The water molecules in the centre of the pipette or burette are heavier, so they sink
deeper than the molecules along the sides of the glassware.
d. The anions and the cations in solution repel each other, forcing them to rise up the
sides of the glass against the force of gravity.
e. The surface tension of water collapses in thin tubing, leading to “sagging” in the
middle of a burette or pipette.
- Complete this sentence: Hexagonal close packed structure result in a packing order of
(i) and atoms with a coordination number of (ii).
(i) (ii)
a. ABABAB 12
b. ABABAB 6
c. ABCABC 6
d. ABCABC 8
e. ABCABC 12
- Which of the following will have the highest vapour pressure at room temperature?
a. pentane, CH 3 CH 2 CH 2 CH 2 CH 3
b. hexane, CH 3 CH 2 CH 2 CH 2 CH 2 CH 3
c. heptane, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3
d. octane, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3
e. nonane, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3
- When the following substances solidify, what type of solid will each one form?
SiO 2 Rh CS 2 Ba 3 N 2
a. ionic molecular molecular network
b. molecular ionic ionic molecular
c. molecular molecular network ionic
d. network metallic molecular ionic
e. network metallic network molecular
Short Answers
- When ionic solids dissolve in water, anions and cations dissociate from the crystal
lattice. What is the strongest interactions experienced by anions and cations in aqueous
solutions?
- Aluminum has a face-centred cubic structure. Aluminum has a radius of 143 pm. What
is the volume of the unit cell of aluminum in units of cm
3 ?
- At 1.00 atm, the boiling point of 2,3,4-trimethypentane, C 8 H 18 , is 113.
° C, and its molar
enthalpy of vaporization is 37.600 kJ mol
- 1 . What is its vapor pressure, in units of bar,
at 105.
° C?
- Bromine is one of only two elements that is a liquid at room temperature. The graph
below shows vapour pressure data for bromine obtained from the CRC Handbook; the
line of best fit has slope = – 4910 K and intercept = 15.2. What are the values of enthalpy
and entropy of vapourization, Δ H vap for bromine?
- A student mixed 5.00 g (0.0594 mol) of solid cyclohexane, C 6
H
, (84.18 g mol
) at its
melting temperature of 6.6°C with 50.0 g (0.594 mol) of liquid cyclohexane at 50.0°C in
an open yet insulated container. After thermal equilibrium was established, the
temperature of the mixture was 44.5°C. The specific heat capacity of liquid cyclohexane
is 1.809 J g
K
, and is assumed to be constant over the temperature interval. From
this information, what is the molar enthalpy of fusion, Δ H fusion
, of cyclohexane?
- You chop out a 500 g sample of ice out of the Red River when it – 40 °C outside, then you
bring the ice sample indoors where it melts and heats up to 25°C. Assuming that Red
River ice is composed of pure water, what is the total energy is absorbed by the ice
sample?
Water Data
Density of water 1.00 g/mL
Heat capacity of ice: 2.09 J g
Heat capacity of liquid water: 4.18 J g
Heat capacity of water vapour: 2.01 J g
Enthalpy of fusion: 6.02 kJ mol
Enthalpy of vapourization: 40.7 kJ mol
Melting point (1 bar): 273 K
Boiling point (1 bar): 373 K
- Strontium titanate is a mineral used in simulated diamonds. Its unit cell is provided
below. What is the empirical formula for this mineral?
Eight Sr atoms reside on the corners
Six O atoms reside on the faces
One Ti atom occupies the centre of
the unit cell
Long Answer
- Silver (Ag) metal has a face-centred cubic unit cell and has a density of 10.59 g/cm
3 .
What is the atomic radius, in pm, of a silver atom?
- a. Indicate with an X which intermolecular force(s) must be overcome when the
following pure liquids are vapourized.
b. In the last column, rank the order of the boiling points for these liquids with numbers
1 – 4 where 1 has the lowest boiling point and 4 has the highest boiling point.
Compound
(dipole-dipole)
dipolar forces
(London dispersion)
dispersion forces
Hydrogen
bonding
Boiling point
order
O
O
HN 2
HN 2
OH
- How much energy is required to heat 36.0 g (2.00 mol) H 2 O from a liquid at 65°C to a gas
at 115°C?
Water Data
Density of water 1.00 g/mL
Heat capacity of ice: 2.09 J g
Heat capacity of liquid water: 4.18 J g
Heat capacity of water vapour: 2.01 J g
Enthalpy of fusion: 6.02 kJ mol
Enthalpy of vapourization: 40.7 kJ mol
Melting point (1 bar): 273 K
Boiling point (1 bar): 373 K
- Use the phase diagram below to answer the following questions.
a. Label points x, y and z in the phase diagram.
b. At what temperature does the substance vaporize at 0.5 0 atm?
c. Does the substance sublime under normal conditions? Explain.
d. At what temperature and pressure does a supercritical fluid form?
c. No. Explanation that shows a student understands normal conditions and
how to read a phase diagram.
d. T = 2 25 °C, P = 1.25 bar
