Use the Force
(of Attraction)
(of Attraction)
Which intermolecular force occurs between all molecules?
London Dispersion Forces (LDFs)
Which property of liquids refers to the resistance to flow?
Viscosity
Which gas law states that pressure is directly proportional to temperature (constant volume and moles).
Gay-Lussac's Law
There are 4 postulates to the Kinetic Molecular Theory. Two have been listed below. What are the other two postulates?
1. The volume of particles is negligible.
2. Particles are in constant motion; collisions are perfectly elastic
3. There are no intermolecular forces acting between the particles.
4. Average kinetic energy is directly proportional to the Kelvin temperature.
A gas is compressed, which causes its volume to decrease. According to Boyle's Law, what will happen to the pressure of the gas if the temperature remains constant?
Pressure will increase.
Hydrogen bonding can only occur when a hydrogen atom is bound to specific atoms. Name all of them.
Nitrogen, Oxygen, Fluorine
Which type of crystalline solid has extremely high melting points and hardness?
Network Atomic (Covalent) Solids
At STP, what is the volume of 4.5 mol H2?
100.8 L
What is the kinetic energy of 1 mole of oxygen gas at 300 K?
KE = 3RT/2
KE = 3741.3 J/mol
The hydrogen bonds that form between water molecules push the molecules into a crystalline lattice structure when frozen, which leaves more space between molecules than in the liquid state.
Which IMF is the strongest that occurs between molecules of water and methane?
Induced Dipole Forces
Which type of solid does not conduct electricity as a solid, but does conduct electricity as a liquid or an aqueous solution?
Ionic Solids
A 2500 mL container holds 4.25 moles of nitrogen gas at a temperature of 25°C. What is the pressure inside the container? (Round to two decimal places)
PV = nRT
P = 41.57 atm
What is the average velocity of a sample of carbon dioxide at a temperature of 472 K? (Round to two decimal places)
urms = √(3RT/MM)
urms = 517.20 m/s
In general, network atomic solids do not conduct electricity. What is the one exception mentioned in class and why is it able to do this?
Graphite. The structure is made of sheets of carbon that are not bound together, leaving some electrons free to move between the sheets.
Put the following molecules in order from weakest to strongest IMFs:
Chloromethane (CH3Cl)
Hydrofluoric Acid (HF)
Oxygen (O2)
Water (H2O)
O2 < CH3Cl < H2O < HF
What are the two types of metallic alloys and how are they different?
Substitutional Alloy - Atoms of each metal are similar in size. Some atoms of one metal are replaced by atoms of another.
Interstitial Alloy - Atoms of each metal vary in size. The smaller atoms fit between the larger atoms.
What is the density of sulfur hexafluoride at STP? (Round to two decimal places)
MM = dRT/P
d = 6.52 g/L
Nitrogen gas and an unknown diatomic gas are at the same temperature. Given that the rate of effusion of nitrogen gas is 1.59 times faster than the rate of the unknown gas, determine the identity of the unknown gas.
Rate1/Rate2 = √(MM2)/√(MM1)
MM2 = 70.84 g/mol
Unknown Gas = Cl2
The Combined Gas Law is formed by combining which three gas laws? Give the name and equation for each law.
Boyle's Law: P1V1 = P2V2
Charles' Law: V1/T1 = V2/T2
Gay-Lussac's Law: P1/T1 = P2/T2
Explain why cooking oil has a high boiling point than water.
Oil molecules are relatively large, which means there are many places that LDFs can occur. Because of this, the collective LDFs that exists between the oil molecules are stronger than the hydrogen bonds that exist in water. Stronger IMFs = higher boiling point.
Cohesive force: IMFs acting between the molecules of the liquid.
Adhesive force: IMFs acting between the molecules of the liquid and the container.
A mixture of 0.25 mol He, 0.15 mol Ne, and 0.3 mol Ar is contained in a 10 L vessel at 27°C.
Calculate the partial pressure of each gas and the total pressure exerted by the mixture. (Round to 2 decimal places)
PTot = PA * XA
PHe = 0.61 atm; PNe = 0.37 atm; PAr = 0.74 atm
In what two situations does the behavior of real gases differ significantly from the expected ideal behavior? Explain why this occurs for each situation.
1. High Pressure - Molecules are closer together which allows for stronger IMFs to take effect.
2. Low Temperature - Average kinetic energy decreases in low temperatures which means IMFs have a stronger effect on a large portion of the molecules.
Cornstarch has several areas that allow hydrogen bonding. When force is applied to oobleck, the cornstarch molecules are pushed closer to the water molecules which creates several temporary hydrogen bonds.