PRACTICE TEST – Inter Molecular Forces
Name: __Answer Key_______
Identify each as either ionic or covalent compounds and provide either the name or formula 6 points
You may find these prefixes
helpful for the questions below
Name or Formula
ex) nitrogen trihydride
ex) (NH4)2CO3
1) calcium hydroxide
mono-
di-
tri-
tetra-
penta
hexa-
hepta
octa-
nona-
deca-
1
2
3
4
5
6
7
8
9
10
Ionic or
Covalent
Covalent
Cation & Anion
N/A - Covalent
NH3
Ionic
2 NH41+ 1 CO32-
Ammonium Carbonate
Ionic
Ca2+
1
2) CO
Covalent
3) carbon tetrahydride
Covalent
2
Name or Formula
(also known as ammonia)
OH1-
Ca(OH)2
N/A
Carbon Monoxide
N/A
Fe3+
CH4
1-
4) Iron (III) Nitrate
Ionic
1
5) MgSO4
Ionic
1 Mg 2+ 1 SO42-
Magnesium Sulfate
6) Co(OH)2
Ionic
1 Co2+ 2 OH1-
Cobalt (II) Hydroxide
3 NO3
Fe(NO3)3
Ionic compounds need to have a Net Charge of ZERO
Identify each of the Bond Types as either: Nonpolar Covalent, Polar Covalent, or Ionic
(Do not forget to include the identification of cations and anions or partial positive and partial negative where appropriate.)
(for ionic)
(for polar covalent)
6 points
7) HO
H
2.2
ΔEN =
O
3.5
8) HI
1.3
H
2.2
Polar Covalent
(Identification)
9) (+) MgO (-)
10)
NH
I
2.5
ΔEN =
0.3
Nonpolar Covalent
(Bond Type)
Ionic
Polar Covalent
11)
12)
(Identification)
HF
O-O
(Bond Type)
Polar Covalent
Nonpolar covalent
13) Complete the Lewis Structures for each compound below, but sure to show the electrons for each atom
and how the valence electrons overlap to indicate each covalent bond. 6 points
O2
CH3OH
SiO2
O
O
O
O
O=O
Polar or Nonpolar
Si
O
O
O
Si
O
O = Si = O
Polar or Nonpolar
Hx
O
C H x Hx
H
x
x
H C Ox H
x
H
Hx
Polar or Nonpolar
14) For each item above (#13), indicate (circle) if the molecule is a polar molecule or non-polar molecule
15) Circle the molecular structure of CH3OH
18) Explain “how” atoms become partially positive and partially negative in a polar bond. 2 points
In a polar covalent bond, the electrons are shared unequally. The atom with
the higher electronegativity will have a higher tendency to attract the shared
bonding electrons. These negatively charged electrons will create a partially
negative charge around the atom with the higher electronegativity. The other
bonded atom will become partially positive.
Match each item (a-o) with the correct statement below.
(NOTE: each item (a-o) may be used once, more than once, or not at all).
a.
b.
c.
d.
e.
cation
anion
electrostatic force
electronegativity
dipole (polar molecule)
f.
g.
h.
j.
k.
ionic bond
polar covalent bond
nonpolar covalent bond
intramolecular force
intermolecular force
10 points
l. Van der Waals force
m. London dispersion force (LDF)
n. dipole-dipole interaction (DDI)
o. hydrogen bond (HF)
_c_ 19. the force of attraction between a positive and negative charge
_j_ 20. the electrostatic force between atoms – (polar covalent, nonpolar covalent, metallic, ionic)
_k_ 21. the electrostatic force between molecules – cause molecules to stick to each other
_a_ 22. atom or group of atoms having a positive charge
_n_ 23. intermolecular force between molecules that have permanent dipoles that are attracted to each other
_d_ 24. the relative ability of a bonded atom of an element to attract the electrons from the another element participating
in the bond.
_e_ 25. a molecule that has two electrically charged regions (a slightly positive region and a slightly negative region)
_m_ 26. these forces are present in all molecules, whether they are polar or nonpolar.
_f_ 27. the electrostatic force of attraction binding oppositely charged ions together
_g_ 28. a covalent bond between two atoms of significantly different electronegativities – (bonding occurs when the
electrons are shared unequally.)
_b_ 29. atom or group of atoms having a negative charge
_h_ 30. a covalent bond between atoms where the bonding electrons are shared equally.
_m_ 31. intermolecular force between an instantaneous dipole and an induced dipole. (Caused by the motion of the
electrons)
_o_ 32. this type of intermolecular force is found between molecules of water (H2O)
_o_ 33. the dipole-dipole interactions experienced between molecules when H is bonded to N, O, or F
_d_ 34. in a polar covalent bond, the atom with the higher ___________ will become partially negative
_l__ 35. the weak attractive forces that hold molecules together (includes London dispersion, dipole-dipole interactions
and hydrogen bonds)
_c_ 36. the force of attraction within ionic, metallic, and covalent bonds, hydrogen bonds, dipole-dipole interactions,
London dispersion forces, and even between protons & electrons is due to ________. (pos & neg)
Identify each of the following as either intermolecular or intramolecular
4 points
37) _ intramolecular__ Polar Covalent Bond
40) _ intramolecular__ Ionic Bond
38) _ intermolecular__ Hydrogen Bond
41) _ intermolecular__ Dipole-Dipole Interact
39) _ intermolecular__ London Dispersion
42) _ intermolecular__ Van der Waals
42) For each box below, identify (label) the intermolecular and intramolecular attractions
4 points
Intermolecular
Intermolecular
Intramolecular
_a_
43) Which of the following covalent bonds is the most polar?
a. H—F
b. H—C
c. H—H
d. H—N
_c_
44) Which of the following atoms acquires the most negative charge in a covalent bond with hydrogen?
a. C
b. N
c. O
d. S
_b_
45) Which of the forces of molecular attraction is the weakest?
a. dipole-dipole interaction b. London dispersion c. hydrogen bond
Intramolecular
d. single covalent bond
_d_
46) Why do atoms share electrons in covalent bonds?
a. to become ions and attract each other
c. to become more polar
b. to gain a higher electronegativity
d. to attain a full valence energy level
_c_
47) A bond formed between a silicon atom and an oxygen atom is likely to be ____.
a. ionic
b. coordinate covalent
c. polar covalent
d. nonpolar covalent
_b_
48) What is thought to cause the London dispersion forces?
a. attraction between ions
c. sharing of electron pairs
b. motion of electrons
d. differences in electronegativity
_a_
50) Why is hydrogen bonding only possible with hydrogen?
a. Hydrogen’s nucleus is electron deficient when it bonds with an electronegative atom.
b. Hydrogen is the only atom that is the same size as an oxygen atom.
c. Hydrogen is the most electronegative element.
d. Hydrogen tends to form covalent bonds.
Identify the primary type of Van der Waals Forces that exist between each type of molecule:
LDF = London Dispersion Forces, DDI = Dipole-Dipole Interaction, HB = Hydrogen Bonds
51)
C2H5OH- _HB__
52)
CH3Br- _LDF__
53)
HI-
54)
CCl4-
_LDF__
55)
CH3NH2 -_HB__
56)
CO2-
_LDF__
57)
Ar-
_LDF__
58)
HF -
_DDI__
59)
C2H4O - _DDI__
60)
Br2-
_LDF__
_LDF__
10 points
63) List and explain the two factors that affect the force of attraction in London dispersion forces?
Size – the larger the molecule, the more electrons there are, the stronger the
temporary dipole, the stronger the London dispersion force (=higher BP)
Shape –the greater the surface area in contact between the molecules, the stronger
the London dispersion force. (Longer, skinny molecules can allow for more
surface area in contact between molecules and will have stronger forces)
64) Explain how London dispersion forces cause molecules to be attracted to one another.
Due to the motion of the electrons - the electrons can move so that a majority of the
electrons are on one side, creating a partial negative side and the opposite side
becomes partial positive (an instantaneous dipole). This instantaneous dipole can
cause an adjacent molecule to induce a second dipole. The electrostatic force of
attraction between the partial positive of one dipole is attracted to the partial negative
of the second dipole resulting in a London dispersion force between the two particles.
65) Rank the following FOUR molecules from lowest to highest boiling points: EXPLAIN
CH4 (1)
CBr4 (4) CCl4 (3) CF4 (2)
LDF
LDF
LDF
LDF  All LDF
2 points
The larger the molecule, the stronger the LDF, the higher the boiling point
66) Rank the following THREE molecules from lowest to highest boiling points: EXPLAIN 2 points
 All LDF
LDF (3)
LDF (2)
LDF (1)
The larger the molecule, the stronger the LDF, the higher the boiling point
67) Rank the following THREE molecules from lowest to highest boiling points: EXPLAIN 2 points
DDI
(2)
HB
(3)
LDF
(1)
LDF forces are the weakest, and HB are the strongest  stronger forces = higher boiling points
68) What is the difference between a hydrogen bond and a polar covalent bond involving hydrogen?
A hydrogen bond is an INTERMOLECULAR force between MOLECULES
where the molecules have a hydrogen atom covalently bonded to either a
Nitrogen, Oxygen, or Fluorine atom.
A polar covalent bond is an INTRAMOLECULAR force between the ATOMS
where a hydrogen atom (EN=2.2) is bonded to another nonmetallic atom with
an electronegativity greater than 2.6 (ΔEN greater than 0.4 = polar covalent)
69) Complete the table below using the following terms: (Solid, Liquid, Gas, Exothermic, Endothermic)
Phase Change
From
To
Endothermic or Exothermic
Deposition
Gas
Solid
Exothermic (Gas is losing energy)
Sublimation
solid
gas
Endothermic
Freezing
liquid
solid
Exothermic
Melting
solid
liquid
Endothermic
Condensation
gas
liquid
Exothermic
Vaporization
liquid
gas
Endothermic
70) TRUE or FALSE: Gases have an indefinite shape and a definite volume.
71) TRUE or FALSE: The motion/speed of the particles increases as the temperature of particles decreases.
72) TRUE or FALSE: Because the shape of a solid never changes, the particles of the solid do not move.
73) TRUE or FALSE: Particles can stick together because of the intermolecular forces between the particles.
74) TRUE or FALSE: It is possible to heat pure water to a temperature of 127 °C.
75) TRUE or FALSE: Energy is either absorbed (Exothermic) or released (Endothermic) during a phase change.
76) TRUE or FALSE: The temperature of a substance changes during a phase change (melting/boiling).
77) TRUE or FALSE: The freezing point of and the melting point of a substance is the same temperature.
78) You put your recently washed, wet clothes into the dryer and start the machine. Forty-five minutes later,
your clothes are dry. What happened to the water?
ENERGY moves
Causing the SPEED
This will cause the particles to
dryer
from the _____________
of the particles to
become more (held together,
water
to the _______________
move (slower, faster) separated).
(ATTRACTION)
Resulting in a PHASE CHANGE
from a (s,l,g) to (s,l,g) which is called
vaporization
_______________ and is (Endo, Exo)
79) A piece chocolate is sitting on the dashboard of your car on a hot sunny day.
ENERGY moves
Causing the SPEED
This will cause the particles to
sun
from the _____________
of the particles to
become more (held together,
chocolate
to the _______________
move (slower, faster) separated).
(ATTRACTION)
Resulting in a PHASE CHANGE
from a (s,l,g) to (s,l,g) which is called
melting and is (Endo, Exo)
_______________
80) After taking a hot shower, the mirror in the bathroom is all steamy (covered in water droplets). Explain
how the mirror became wet. (Be sure to use the proper scientific terms in your response)
Liquid water from the shower evaporated (turned into a gas = water vapor)
and traveled throughout the bathroom. When this higher energy gas came into
contact with the colder mirror, it transferred some of this energy to the colder
mirror. By losing this energy, the gaseous water vapor underwent a phase
change from a gas into a liquid (condensing on the mirror as liquid water).
81) EXPLAIN what is happening at the atomic level when a substance undergoes a phase change? Details required.
During a phase change particles (molecules) of a substance will either:
1) Gain energy, move faster, and start to overcome the intermolecular forces
holding the particle together. This would be an endothermic phase change.
2) Lose Energy, move slower, and start to be held more closely together by the
intermolecular forces between the particles - an exothermic phase change.
(OR – You could have picked a type of phase change and described it)