Chem 3 Exam Review

Intermolecular Forces

Forces between molecules; bonds are within molecules.

Which is stronger, bonds or intermolecular forces?

Bonds.

List the intermolecular forces on increasing strength…

Dispersion forces —> Dipole-dipole forces —> Hydrogen Bonding —> Ion-Dipole forces.

Dispersion forces

Between all neutral particles but are the only intermolecular forces between non-polar molecules.

Dipole-dipole forces

Between particles with permanent dipole (polar molecules).

Hydrogen bonding

Between particles w/ N-H, O-H, and F-H bond. Strongest intermolecular force in a pure substance.

Ion-dipole force

Between polar molecules and ions (for example, when dissolving an ionic compound in water).

Polar solvents dissolve…

Polar or ionic solutes.

Non-polar solvents dissolve…

Non-polar solutes.

With all other properties being equal as molar mass increases, what else increases?

Viscosity, boiling point, melting point.

With all other properties being equal as intermolecular forces increase, what else increase?

Surface tension, boiling point, melting point, and viscosity.

Valence Bond Theory

A chemical bond is the overlap of two-half filled atomic orbitals from two adjacent atoms and spin-pairing electrons.

What determines the molecular geometry in valence bond theory?

The geometry of the overlapping orbitals.

The shapes and energies of the atomic orbitals combined determine…?

The shapes and energies of the hybrid orbitals.

#standard atmoic orbitals added together - #hybrid orbitals formed =

Are hybrid orbitals degenerate?

True

4 sp3 orbitals have…?

An energy which is the average of the s and 3 p orbitals used to make them.

Hybrid orits have a _____ lobe and ____ lobe.

Major, Minor

Which lobe is pointed toward the four corners of a tetrahedron for sp3 hybridization. (Used for tetrahedral electron geometry)

Major lobe.

Sigma Bond

Shares electron density on the line that connects the two nuclei.

Pi bond

Shares electron density not on the line that connects.

All bonds have what one type of component?

Each has one sigma component.

Additional components are sigma or pi?

Pi components.

Single bonds

1 sigma component, 0 pi components.

Double bonds

1 sigma component, 1 pi component.

Triple bonds

1 sigma component, 2 pi components

Interior atoms

Sigma component uses hybrid orbital

Peripheral atoms

H uses a half-filled s atomic orbital; all other non-metals will use half-filled p orbitals

Hybridization is appleid to…

Interior atoms only.

To determine the hybridization…?

Count the number of electron groups around the interior atoms; this is the number of hybrid orbitals needed.

When combing atomic orbitals…?

Start with the lowest energy orbitals.

Order for writing hybridization…?

1 s orbital —> up to 3 p orbitals —> d orbitals.

Orbital

The volume that encompasses 90% of the probability of where an electron is likely to be found when modeled as a standing wave around the nucleus.

Molecular Orbital Theory

Delocalize the electrons by modeling them as standing waves around multiple atoms in a molecule, thus creating molecular orbitals as opposed to atomic orbitals.

Trial functions

The guess that is substituted in for Schrödingers equation.

What is linear combination of atomic orbitals (LCAO) used for?

To come up with a trial function.

How do we create molecular orbitals?

Adding together standard atomic orbitals from multiple different atoms in a molecule.

Constructive Interference

By adding orbitals together, anywhere electron density overlaps from the two orbitals.

Destructive Interference

By subtracting orbitals, anywhere electron density overlaps.

Bonding molecular orbital

Constructive interference, lower in energy than antibonding.

Antibonding molecular orbital

Destructive interference, higher in energy than bonding.

How to form and find molecular orbital diagram?

Combine two atomic orbitals of different atoms to produce two molecular orbitals that span the entire molecule. A bonding and a antibonding molecular orbital is created.

Bond Order

( (# e- in bonding MO) - (# e- in antibonding MO) ) /2

What does a positive bond order indicate?

The molecule or polyatomic ion should be stable enough to exist under certain conditions

What does a bond order of 0 indicate?

It is not energetically favorable to form the molecule, it should not exist.

What does the higher the bond order mean?

The stronger the bond is.

Chemical Change

Alters the identity of the substance through the arrangement of atoms and bonds.

Physical Change

Does not alter the identity of the substance.

Chemical Property

Can only be observed by changing the identity of the substance.

Physical Property

Can be observed without changing the identity of the substance.

Rusting

A chemical change, identities of the H2O molecules change.

Boiling

Boiling is a physical change, identities of the H2O molecules don’t change.

Limiting reagent (Limiting reactant)

Runs off first and limits the amount of product that can be produced.

Theoretical yield

the amount of product that can be produced from the limiting reagent.

Actual yield

The amount of product produced when running the experiment.

Percent yield

actual yield/theoretical yield x 100%

Combustion Reaction

Involves a substance reacting with oxygen to form one or more oxygen-containing compounds.

In presence of sufficient oxygen, carbon forms…

Carbon Dioxide

In presence of sufficient oxygen, hydrogen forms…

Water Vapor

In presence of sufficient oxygen, sulfur forms…

Sulfur Dioxide

In presence of sufficient oxygen, nitrogen forms…

Nitrogen Dioxide

Alkali Metal Reactions

2 M + X2 → 2 MX

Halogen Reactions

2 M + n X2 → 2 MXn

Molarity

moles of solute/ liters of solution

Stock solutions

Chemical solutions stored in highly concentrated form.

Relatively strong solvent-solute interactions do what?

They promote the process of dissolving.

Soluble Ionic Compounds

Strong electrolytes, producing cations and anions when dissolved in solution.

Strong Acids

Strong Electrolytes: HCL, HBr, HI, HNO3, HClO4, and first H in H2SO4. Good conductors.

Weak Electrolytes

Only weak conductors, a weak acids is an example. It only ionizes to a very small extent.

Nonelectrolytes

May dissolve in solution, but they do not form ions so they cannot carry a current. Examples: Sugar, C2H5OH, C6H5

Precipitation Reactions

Two soluble ionic compounds combine to produce an insoluble ionic compound.

Molecular Equation

Shows strong electrolytes as compounds.

Complete Ionic Equation

Shows strong electrolytes broken apart into their component ions.

Net Ionic Equation

Removes spectator ions, which show up the same on both reactants and products side of equation.

Arrhenius Acid

Produces H+ in solution.

Arrhenius Base

Produces OH- in solution.

HCl

Hydrochloric acid (strong)

HBr

Hydrobromic acid sStrong)

HI

Hydroiodic acid (strong)

HNO3

Nitric acid (strong)

H2SO4

Sulfuric acid (strong)

HClO4

Perchloric acid (strong)

HC2H3O2

Acetic acid (weak)

HF

Hydrofluoric acid (weak)

NaOH

Sodium hydroxide (strong)

LiOH

Lithium hydroxide (strong)

KOH

Potassium hydroxide (strong)

Ca(OH)2

Calcium hydroxide (strong)

Ba(OH)2

Barium hydroxide (strong)

NH3

Ammonia (weak)