Chapter 12

3-2-1 WOC : Water
3 – Identify three “unique” properties of water.
2 – Describe how the “polar” nature of the water
molecule contributes to two of the “unique”
properties of water you listed.
1 – State one environmental impact that results
from water being an “universal” solvent.
Hydrogen “bond” – an additional attractive
force (dipole-dipole electrostatic attraction)
- much weaker than ionic or covalent bonds
Usually seen with compounds that contain H
covalently bonded to F, O, or N.
Typically, N-H and/or O-H, rarely F-H
Represented by (….)
Hydrogen bonds can be intermolecular (between
molecules) and/or intra-molecular (structural
folding, i.e. proteins, DNA…)
 51. Explain the difference between a temporary dipole and a
permanent dipole.
A temporary dipole forms when one molecule is close to
another molecule and the electrons repel each other creating
a greater electron density in one part of the molecule.
Permanent dipoles are found in polar molecules in which
some regions of the molecule are always partially positive and
partially negative.
 52. Why are dispersion forces weaker than dipole-dipole
Dispersion forces are between temporary dipoles.
Dipole-dipole forces are between permanent dipoles.
 53. Explain why hydrogen bonds are stronger than most
dipole-dipole forces.
A hydrogen bond involves a large difference in electronegativity
between the hydrogen atom and the atom it is attached to (O,N,F),
making the bond extremely polar.
 54. Compare intramolecular and intermolecular forces.
Intramolecular forces hold atoms together in a molecule while
intermolecular forces hold different molecules together.
 55. Hypothesize why long, nonpolar molecules would
interact more strongly with one another than spherical
nonpolar molecules of similar composition.
Because long molecules have greater surface areas, more
intermolecular forces can exist.
 56. Use relative differences in electronegativity to label the
ends of the polar molecules listed as partially positive or
partially negative.
 A. HF
 B. HBr
H – Br
 C.NO
 D. CO
δ+ δ-
 57. Draw the structure of the dipole-dipole interaction
between two molecules of carbon monoxide.
 58. Decide which of the substances listed can form
hydrogen bonds.
 A. H2O
 B. H2O2
 C. HF
 D. NH3
All of the substances above can form hydrogen bonds.
 59. Decide which one of the molecules listed below
can form intermolecular hydrogen bonds, and then
draw it, showing several molecules attached together
by hydrogen bonds.
 A. NaCl
 B. MgCl2
 C. H2O2
 D. CO2

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