AP Chemistry Thou Shalt Not Forget Factoids UNIT 3

What are the types of intermolecular forces (IMFs) from weakest to strongest?

1. London Dispersion 2. Dipole-Dipole 3. Hydrogen Bonding 4. Ion-Dipole

What happens to London Dispersion forces as the size of the molecule increases?

London Dispersion forces get stronger as the molecule is larger due to a larger electron cloud that makes it more polarizable.

Which molecules contain dipole-dipole forces and how does this force change?

All polar molecules contain dipole-dipole forces, and this force increases as the molecule becomes more polar.

What is the definition of hydrogen bonding in the context of intermolecular forces?

Hydrogen bonds occur between a nitrogen, oxygen, or fluorine (NOF) atom in one compound to a hydrogen that is already bonded to a NOF in another compound.

How do boiling points and melting points relate to the strength of IMFs?

Boiling points and melting points increase as the strength of IMFs increases.

What is the relationship between vapor pressure, volatility and IMFs?

Vapor pressure and volatility decrease as the strength of IMFs increases.

What are the characteristics of molecular solids?

Molecular solids have low melting/boiling points and do not conduct electricity.

How do ionic solids conduct electricity?

Ionic solids have high melting/boiling points and do not conduct electricity as a solid but do conduct as a liquid or in aqueous solution.

What are the properties of covalent network solids, specifically SiO2 (quartz) and diamonds?

Covalent network solids such as SiO2 (quartz) and diamonds have very high boiling/melting points.

What are the properties of metallic bonds?

Metallic bonds are between metals, they always conduct electricity, and their hardness varies.

What breaks when a molecular solid melts or boils?

When a molecular solid melts or boils, it is the IMFs between the molecules that break, not the covalent bonds.

What are interstitial and substitutional alloys?

1. Interstitial alloys are made when a smaller atom fits into the gaps between larger atoms of a metallic crystal. 2. Substitutional alloys are formed when the radii of the metals are similar in size and are substituted into the crystal lattice.

Why are gas mixtures considered homogeneous?

Gas mixtures are homogeneous because of the constant random motion of the particles.

Why are gases compressible?

Gases are compressible because of the large spaces between the particles.

What causes gas pressure?

Gas pressure is caused by collisions of particles with the walls of the container.

What is the relationship between pressure and volume?

Pressure (P) and volume (V) are inversely related; doubling the volume of a container will cut the pressure of the gas in half.

What is the relationship between temperature and volume?

Temperature (T) and volume (V) are directly related; heating a balloon will cause it to expand.

What is the relationship between temperature and pressure?

Temperature (T) and pressure (P) are directly related; heating a rigid container will increase the pressure of the gas.

What is the ideal gas law?

PV=nRT, where P is pressure, V is volume, n is number of moles, R is the gas constant (R=0.08206), and T is temperature in Kelvin.

How does gas pressure relate to the number of moles?

Gas pressure and the number of moles are directly related; doubling the moles of gas in a container will double the pressure.

How do you calculate molar mass using the ideal gas law?

Molar mass can be calculated using the formula: Molar Mass = dRT/P, where 'd' stands for density in g/L.

How does molar mass affect the speed of gas moving at a given temperature?

The more molar mass a gas has, the slower it moves at a given temperature.

How is temperature related to average kinetic energy?

Temperature is a measure of average kinetic energy; gases at the same temperature have the same average kinetic energy.

What is the equation for total pressure when collecting a gas by water displacement?

Ptotal = Pdry gas + Pwater vapor.

Under what conditions do real gases behave most like ideal gases?

Real gases behave most like an ideal gas at high temperature and low pressure.

What causes gases to deviate from ideal behavior?

Real gases deviate from ideal behavior the more polar they are and the larger they are; small, nonpolar gases are the most ideal.

How does filtering separate mixtures?

Filtering separates mixtures based on differences in particle size; large particles are trapped on the filter paper while the soluble component goes through.

How does distillation separate mixtures?

Distillation separates mixtures based on differences in boiling points.

How does chromatography separate mixtures?

Chromatography separates mixtures based on differences in polarity.

In paper chromatography, how does the polarity of a component affect its movement?

The component that is most similar in polarity to the 'mobile phase' moves up the farthest.