IMF 1
IMF 2
IMF 3
Solid States
Past Material
100
What forces occur in all substances?
London dispersion forces
100
What are the 3 intermolecular forces in order of increasing strength?
-London dispersion forces
-dipole-dipole
-Hbond
100
How are boiling points affected by intermolecular forces?
Stronger intermolecular forces between molecules make it more difficult for those molecules to be pulled apart. Therefore, stronger intermolecular forces result in higher boiling points.
100
What are the four types of crystalline solids?
Ionic: solid structure composed of ions arranged in a 3D structure and held together by ionic bonds (e.g., CaCl2);
Molecular: solid structure composed of covalent molecules held together by intermolecular forces (e.g., ice);
Covalent network: solid structure made up of covalently bonded atoms in a 3D arrangement (e.g., diamond);
Metallic: 3D arrangement of metallic atoms held together by a cloud of electrons over the array of atoms (e.g., steel)
100
Record the volume
43.0 mL
200
Define a dipole-dipole interaction? What type of molecule does it need to be?
_attractive forces between polar molecules (pure substance or mixture)__
200
Which elements bonded with hydrogen create an H bond?
FON
200
List the following molecules in order of increasing boiling point: Br2, F2, I2, Cl2,
F2, Cl2, Br2, I2
200
Rank the 4 crystalline solids in increasing strength
molecular < ionic ~ metallic < covalent network
200
What element is represented by the following PES graph?
Phosphorus
300
As intermolecular forces increases vapor pressure _____
decreases
300
What are the IMF's
H2
Just London!
300
Which of the following
molecules can form
hydrogen bonds?
H2 CH4 NH3 HF CH3OH
NH3 HF CH3OH
300
What type of solid are the following substances
KCl
SF2
NH4NO3
Cu
KCl - ionic
SF2 - molecular
NH4NO3 - ionic
Cu - metallic
300
What bond angle would be present for a molecule with 4 regions of electron density (3 bonds, 1 lone pair)?
<109.5
400
Which substance would have the greater intermolecular forces
SeO2 or SO2
SeO2 and SO2 are both polar, but the dipoles are stronger in SeO2, so it has stronger IMF’s.
400
List all the IMF's in
HBr and HF
HBr - london dispersion forces, dipole dipole attractions
HF - hydrogen bonding, london dispersion, dipole dipole
400
What holds molecules of water together?
What holds the O and H atoms together in one molecule of water?
Hydrogen bonding
Polar covalent bonds
400
Arrange the order of
melting points for the
following solids,
highest to lowest:
CH4 C6H14 C2H6 C4H10
C6H14 > C4H10 > C2H6 >CH4
400
Which electron would be easier to remove, one located in n=5 energy level or n=2 energy level? Explain in terms of Coulomb's law.
Electron in the 5th energy level. This electron is further from the nucleus, therefore, it has less Coulombic attraction to the nucleus making it easier to remove.
500
Define surface tension and viscosity. How do intermolecular forces affect these properties (i.e., as intermolecular forces increase, what happens to each property?
Surface tension is the resistance of a liquid to spread out. Viscosity is a measure of a substance’s resistance to flow. As the strength of IMF’s increase, surface tension and viscosity increase. Molecules are more strongly attracted to each other and will be less likely to spread apart or to flow.
500
NaCl has a melting point of 801 oC
KCl has a melting point of 776 oC
Explain the difference in melting point AND which has a greater lattice energy.
The charges on the ions are the same in both compounds, but the Na+ ion has a smaller radius than the K+ ion, which makes the lattice energy of NaCl greater than that of KCl. This means more energy is required to overcome the forces in NaCl than in KCl; thus NaCl will have a higher melting point.
500
List the following molecules in order of increasing surface tension: C3H8, CH4, CH3COOH, C2H6
Higher surface tension corresponds to stronger intermolecular forces. Go through the list above.
1. One of these (CH3COOH) has the ability to hydrogen-bond. It will probably have the strongest intermolecular forces.
2. CH3COOH is the only one of these molecules to have a dipole, and we already decided it hasthe strongest intermolecular forces.
3. Of the molecules that are left, the largest one (C3H8) likely has the strongest London dispersion forces. The smallest (CH4) likely has the weakest intermolecular forces. The answer is: CH4, C2H6, C3H8, CH3COOH
500
While network solids are rigid and hard, why is graphite soft?
Three-dimensional network solids are rigid and hard, because the covalent bond angles are fixed.
However, graphite is soft because adjacent layers can slide past each other relatively easily.
500
Determine the empirical formula for the compound with the following percent composition:
15.8% carbon and 84.2% sulfur
CS2