Gen Chem 2

__1.13.23

__Intermolecular Forces are attractive forces between molecules (weaker than intra). They measure boiling point, melting point, change in heat of vapor, and change in heat of fusion.

Intramolecular forces hold atoms together in a molecule.

Dipole-Dipole Forces: attractive forces between polar molecules.

Ion-Dipole Forces: Attractive forces between an ion and a polar molecule

Not all cations and anions behave the same. The bigger the charge to radius ratio the weaker the interaction.

London Dispersion Forces: Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules (everything will have it)

Induced dipoles: As molecules come closer with lots of electrons the shells can deform.

Polarizability: the ease with which the electron distribution in the atom or molecule can be distorted

Higher intermolecular forces means need more energy needed to break bonds.

Polarizability increases with greater number of electrons and more diffuse electron cloud (size)

Dispersion forces usually increase with molar mass.

Hydrogen bond is a special dipole-dipole interaction between the hydrogen atom in a N-H, O-H, F-H and an electronegative N, O, or F

Properties of Liquid: Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit of area.

Stronger molecular forces = High surface tension

Cohesion: is the intermolecular attraction between like molecules

Adhesion: is an attraction between unlike molecules

Viscosity: a measure of a fluid’s resistance to flow

Crystalline solid: involve repeating patterns of small units (unit cells)

Amorphous solid: does not posses a well-defined arrangement and long-range molecular order.

Unit Cell: basic repeating structural unit of a crystalline solid.

3 types of Cubic Cells, 1. Simple 2. Body-centered 3. Face-centered cubic

Chapter 11 Reading

11.1 The Kinetic Molecular Theory of Liquids and Solids

Great space between gases explains why gases have very low densities under low conditions

There is very little empty space in liquids, they are more compressed than gas, but still move

Molecules in a solid are rigid with no freedom of motion. They have definite shape and size. Even less space then liquids.

Solids are usually more dense than liquids with some exceptions (water.)

A phase is change in matter state.

11.2 Intermolecular Forces

Intermolecular Forces- are attractive forces between molecules

Intramolecular Forces- Hold atoms together in a molecule.

Intramolecular forces are stronger than intermolecular forces.

Intermolecular forces often decide things such as boiling point, melting point, etc..

Dipole-Dipole Forces: are forces between polar molecules

Ion-Dipole Forces: attract an ion and polar molecule to each other

Dispersion Forces: attractive forces that arise as a result of temporary dipoles induced in atoms or molecules. They usually increase with molar mass. They increase in strength with more electrons.

Polarizability: enables gases containing atoms or non polar molecules to condense

Hydrogen Bond: Type of dipole-dipole bond in a polar bond

11.3 Properties of Liquids

Surface tension: amount of energy required to stretch or increase the surface of a liquid

Cohesion: Intermolecular attraction between like molecules

Adhesion: attraction between unlike molecules

Viscosity: liquids resistance to flow the greater the slower it flows

11.4 Crystal Structure

Solids divide in two categories: Crystalline and amorphous

Crystalline-solid: Contain rigid and long-range order.

Unit cell: basic repeating structural unit of crystalline solid

Simple Cubic cell (scc)

Body-centered cubic (bcc) second layer fits into the depressions of the first & second layer

Face-Centered cubic (fcc) There are spheres at the center of each of the six faces of the cube.

Closest packing: the most efficient arrangement of spheres

11.5 X-Ray Diffraction by Crystals

X-ray diffraction: scattering of X ray to crystalline solid

11.6 Types of Crystals

Ionic: Most have high melting points, a strong indication of the cohesive forces holding the ions together

Covalent

Molecular

Metallic

1.20.23

Clausius-Clapeyron Equation in P=-change in heat vap/RT + C

P=(equilibrium) vapor pressure

T= temperature (K)

R= Gas constant (8.314 j/k*mol)

Boiling point is the temperature at which the equilibrium pressure of a liquid is equal to external pressure

Critical temperature is the temperature above which the has cannot be made to liquefy no matter how great the temperature applied

Critical pressure is the minimum pressure that must be applied to bring about liquefication at the critical temperature

“Life’s tough you need to knock yourself out sometimes.” -Knaus 1.20.23

1.23.23

A solution- is a homogenous mixture of 2 or more substances.

The solute- is the substance present in the smaller amounts- the stuff gets dissolved.

The Solvent- the substance present in the larger amount.- The stuff dissolving.

A saturated solution- contains maximum amount of a solute that will dissolve in a given solvent at a specific temperature.

An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.

A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.

Three types of interactions in the solution process: solvent-solvent interaction, solute-solute interaction, solvent-solute interaction.

“Like dissolves like”

Two substances with similar Intermolecular forces are likely to be soluble in each other.

Non polar molecules are soluble in non-polar solvents

polar molecules are soluble in polar solvents

ionic compounds are more soluble in polar solvents

The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.

Molarity (M)= Moles of solute/liters of solution

Molality (m)= moles of solute/mass of solvent

Solubility increases with increasing temperature

Fractional crystallization is the separation of mixture of substances into pure components on the basis of their differing solubilities.

The solubility of a gas in a liquid is proportional to the pressure of the has over the solution

C=kp

1.25.23

Colligative Properties of Nonelectrolyte Solutions

Colligative properties: properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.

Vapor-Pressure Lowering: P1= X1P1

Boiling-Point Elevation Change in T =Kb m

Freezing-Point Depression Change in T= Kf m

Osmotic Pressure Pi=MRT