Chapter 10 : Liquids and Solids
專有名詞 : dipole-dipole interaction/hydrogen bonding/London dispersion force
1. Identify the most important types of interparticle forces present in the solids of
each of the folllowing substances
a. Ar b. HCl c. HF d. CaCl2 e. CH4 f. CO
g NaNO3
2. Predict which substance in each of the following pairs would have the greater
intermolecular forces
a. CO2 or OCS b. SeO2 or SO2 c. CH3CH2CH2NH2 or H2NCH2CH2NH2
d. CH3CH3 or H2CO
e. CH3OH or H2CO
3. In each of the following groups of substances, pick the one that has the given
property. Justify your answer.
a. highest boiling point : HBr, Kr, Cl2
b. highest freezing point: H2O, NaCl, HF
c. lowest boiling point : CH4, CH3CH3, CH3CH2CH3
d. highest boiling point: HF, HCl , HBr
專有名詞: surface tension/ cohesive force/ adhesive force / viscosity
4. A topaz crystal has an interplanar spacing (d) of 1.36Å. Calculate the wavelength
of the X ray that should be used if θ = 15.0o (assume n =1).
專有名詞: unit cell/ amorphous solid/ crystalline solid/
5. Calcium has a cubic closest packed structure as a solid. Assuming that calcium has
an atomic radius of 197 pm, calculate the density of solid calcium.
6. The radius of gold is 144 pm, and the density is 19.32 g/cm3. Does elemental gold
have a face-centered cubic structure or a body-centered cubic structure?
專有名詞: hcp / ccp / substitutional alloy / interstitial alloy
1
Ionic compounds have ionic forces.
Covalent compounds all have London
Dispersion (LD) forces, while polar covalent compounds have dipole forces and/or
hydrogen bonding forces.
For H bonding forces, the covalent compound must have
either a N−H, O−H or F−H bond in the molecule.
2
a. LD only
b. dipole, LD
d. ionic
e.
f. dipole, LD
g. ionic
a.
c. H bonding, LD
LD only (CH4 in a nonpolar covalent compound.)
OCS; OCS is polar and has dipole-dipole forces in addition to London dispersion
(LD) forces. All polar molecules have dipole forces. CO2 is nonpolar and only
has LD forces.
To predict polarity, draw the Lewis structure and deduce
whether the individual bond dipoles cancel.
b. SeO2;
Both SeO2 and SO2 are polar compounds, so they both have dipole forces
as well as LD forces. However, SeO2 is a larger molecule, so it would have
stronger LD forces.
c. H2NCH2CH2NH2; More extensive hydrogen bonding is possible.
d. H2CO; H2CO is polar while CH3CH3 is nonpolar. H2CO has dipole forces in
addition to LD forces.
e. CH3OH; CH3OH can form relatively strong H bonding interactions, unlike H2CO.
3.
Boiling points and freezing points are assumed directly related to the strength of the
intermolecular forces, while vapor pressure is inversely related to the strength of the
intermolecular forces.
a. HBr; HBr is polar, while Kr and Cl2 are nonpolar. HBr has dipole forces unlike
Kr and Cl2.
b. NaCl;
e. CH4;
f.
4.
λ=
HF;
Ionic forces are much stronger than molecular forces.
Smallest, nonpolar molecule so has the weakest LD forces.
HF can form relatively strong H bonding interactions unlike the others.
2 d sin θ
2 × 1.36 × 10 −10 m × sin 15.0 o
= 7.04 × 10 −11 m = 0.704 ∆
=
n
1