Polarity Of Molecules
For each of the following pairs of molecules, determine which is most polar and
explain your reason for making this choice:
1)
carbon disulfide
OR
sulfur difluoride
2)
nitrogen trichloride
OR
oxygen dichloride
3)
boron trihydride
OR
ammonia
4)
chlorine
OR
phosphorus trichloride
5)
silicon dioxide
OR
carbon dioxide
6)
methane
OR
CH2Cl2
7)
silicon tetrabromide
OR
HCN
8)
nitrogen trifluoride
OR
phosphorus trifluoride
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Types of Intermolecular Forces
What is the strongest intermolecular force present for each of the following compounds?
1)
water _____________________________________
2)
carbon tetrachloride _____________________________________
3)
ammonia (NH3)_____________________________________
4)
carbon dioxide _____________________________________
5)
phosphorus trichloride _____________________________________
6)
nitrogen _____________________________________
7)
dihydrogen Sulfide _____________________________________
8)
methane (CH4) _____________________________________
9)
pure copper _____________________________________
10)
Sodium Chloride _____________________________________
11)
Substance
Melting Point, °K
Substance
Melting Point, °K
N2
63.3
Kl
854.15
C2H6
89.85
NaF
1266.15
HCl
158.4
Cu metal
1357
In terms of the types of intermolecular forces in the above substances, explain the trend
in the melting points.
12) Which are stronger intermolecular forces or the bonds that hold atoms together in
the molecules? Explain your reasoning using evidence from the behavior of a common
substance like water.
13) Water will dissolve ionic and polar solutes but not non-polar solutes. Describe how
the polar nature of water molecules causes this.
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Polarity Worksheet Answers
For each of the following pairs of molecules, determine which is most polar and
explain your reason for making this choice:
1)
carbon disulfide
OR
carbon disulfide is nonpolar
2)
nitrogen trichloride
OR
oxygen dichloride
both are polar, but oxygen dichloride is less symmetric than nitrogen
trichloride, making it more polar.
3)
boron trihydride
OR
boron trihydride is nonpolar.
ammonia
4)
chlorine
chlorine is nonpolar
phosphorus trichloride
5)
silicon dioxide
OR
carbon dioxide
It’s a tie, because both are nonpolar
6)
methane
methane is nonpolar
7)
silicon tetrabromide
OR
silicon tetrabromide is nonpolar
8)
nitrogen trifluoride
OR
phosphorus trifluoride
Both are polar and equally symmetric, but the difference in
electronegativity between N-F is less than that between P-F
OR
OR
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sulfur difluoride
CH2Cl2
HCN
© 2007 Cavalcade Publishing; All Rights Reserved
Types of Intermolecular Forces - Solutions
What is the strongest intermolecular force present for each of the following compounds?
1)
water
hydrogen bonding
2)
carbon tetrachloride
3)
ammonia
hydrogen bonding
4)
carbon dioxide
London dispersion forces
5)
phosphorus trichloride
dipole-dipole forces
6)
nitrogen
London dispersion forces
7)
dihydrogen Sulfide
dipole-dipole forces
8)
methane (CH4)
London dispersion forces
9)
pure copper
metallic
10)
sodium chloride
ionic
London dispersion forces
11) N2 and C2H6 are both non-polar and the molecules of each will be attracted by
relatively weak London Dispersion forces. This causes the low melting points,
since C2H6 is a larger molecule the London forces will be larger than for N2
making its melting point a bit higher. HCl and KI are both polar and attracted by
dipole-dipole forces which are stronger than London forces making their melting
points higher. KI is more polar than HCL. NaF is attracted by ionic forces that
are stronger than dipole-dipole. Cu is a pure metal forming a lattice of Cu ions in
a “sea of electrons”, this is a very strong attraction and results in very high
melting points.
12) Bonds between atoms a much stronger than intermolecular forces. This is
evidenced by the melting and evaporating of water. The attraction
between the molecules changes or breaks much more easily causing
phase changes by leaving the water molecule intact.
13) Water is polar and is capable of attracting other polar molecules. Therefore,
when polar or ionic compound are put in water the water molecules can
pull them apart (dissolve) them by dipole-dipole forces. If the substance in
non-polar than there is no attraction to the polar water molecules and the
substance stay intact and separate.
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© 2007 Cavalcade Publishing; All Rights Reserved