General Chemistry 2 Final Exam

Electrochemical devices

Systems that control the electron transfers in Redox processes.

Redox Reaction

In oxidation, one atom gains electrons and one looses electrons.

Atoms that lose electrons are Oxidized.

Atoms that gain electrons are Reduced.

Thermodynamic stability

Measure of how stable a system is with respect to changes in the surroundings. *****

Galvanic Cell

Spontaneous= No energy input needed, makes energy.

Delta G= (-), Product favored

To increase sell potential:

- Make Delta G more negative

- Increase Surface Area

Electrolyte

Conducts electricity in dissolved form (ex: Salt).

Compound

Two or more chemical elements are bonded.

Element

Substance of atoms that all have the same number of protons.

Homogeneous mixture

A homogeneous mixture has the same uniform appearance and composition throughout.

Heterogeneous mixture

A heterogeneous mixture is composed of non-uniform molecules or they have localized regions that all have different properties.

Chemical change

Any change that results in the formation of a new chemical substance.

Physical change

Rearrangement of molecules that does not effect their chemical makeup.

Law of conservation of mass

Kinetic stability

Endothermic

Process of electrons moving from Low potential energy to High potential energy. Gaining heat/energy.

Ex:

Exothermic

Process of electrons moving from high potential energy to low potential energy. Release of heat/energy.

Ex:

Energetic factors

Energetic stability increases with decreasing potential energy.

Delta H

Features to consider:

Bond strength

Chemical composition

Charge distribution

State of matter

Intermolecular Forces

Entropic factors

The stability of a system increases, the larger the number of ways the system has to distribute both its matter and energy.

Delta S

CONFIGURATIONS

Oxidation

Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.

Oxidation state: (# of valence e- on atom)-(# of bonded e- + # of lone pairs)

Increase in Oxidation #= Oxidation

Decrease in Oxidation #= Reduction

Oxidized= Charge is taken

Reduced= Charge is added

Reduction

Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

Cathode

Ionic radius

Increases from left and down.

Bond angles

Equilibrium constant

Reaction quotient when reaction is at equilibrium.

Solubility

"Like dissolves like":

- Polar solvent will dissolve polar or ionic compound.

- Nonpolar solvent will dissolve nonpolar compound.

- Polar solvent WILL NOT dissolve nonpolar compound.

Solvent must be able to interact with molecules.

Size: ****

Acid and Base:****

Hydrophilic

Polar, accepting of water. Will dissolve if hydrophilic region overcomes hydrophobic region.

Hydrophobic

Nonpolar, not accepting of water. Will not dissolve if hydrophobic region overcomes hydrophilic.

Delta G

Delta H

Delta H= Bonds Broken- Bonds Formed

Increase in IMF= Decrease in Delta H= Exothermic

Decrease in IMF= Increase in Delta H= Endothermic

Delta S

Catalyst

Substance that increases the rate of a chemical reaction without undergoing terminate chemical change.

Intermediate

Molecule that appears in the formula, but not in the final product.

Boiling points

Occurs when liquid molecules have enough energy to break free from attractions between the molecules (IMF).

More Carbon atoms= Higher boiling point

Stronger IMF= Higher boiling point

More Branching/ Less Surface Area= Lower boiling point

Boiling point > 25C= liquid

Boiling point < 25C= Gas

Nucleophile

"Nucleus lover", region of high electron density. Must be a region of (-) charge to attract a (+) nucleus.

A full negative charge is stronger than a partial negative charge.

Electrons flow from Nucleophile ----> Electrophile

Stronger base= Better nucleophile

Electrophile

"Electron lover", region of low electron density. Must be a region of (+) charge to attract (-) electrons.

Electrons flow from Nucleophile ----> Electrophile

Cathode

Reduced element.

RED CAT

Anode

Oxidized element.

Electrode

Polar

Molecule with a positive charge and negative charge.

Non-polar

Molecule with similar charges.

Half Reactions

Standard Molar Entropy

Le Châtelier\'s principle

Leo the Lion Gers

Leo: Lose electrons means oxidation

Ger: Gains electrons means Reduction

Oil Rig

Oil: Oxidation is loss

Rig: Reduction is gained

Decomposition

SN1

Unimolecular substitution of a halogen by a nucleophile. A--> ____

Rate is determined by slow step:

R= K[electrophile] ( [Nu] has no effect in Sn1)

- Favors Tertiary (sometimes secondary)

- Forms a Carbon cation, C +

- Favor Polar Protic solvent (H20 stabilizes C+)

- Wants a WEAK Base- I, Cl, Br

- Bulkier the better

- 1st order

- Wants a STRONG LG

Ea goes down, Rate goes up

Inorganic product

= Leaving Group

Weaker the conjugate base, the better the Leaving group.

SN2

Bimolecular, Rate depends on two concentrations.

A+B--->____ or 2A--->____

R= K[electrophile][Nu]

- Favors Primary (can be secondary)

- Wants a Strong nucleophile

- Wants less bulky

- Favors Polar Aprotic (No H-bonding) (DMSO strengthens the nucleophile)

- Second order

- Wants a WEAK LG

Ea goes up, Rate goes down

Primary

Secondary

Trichiary

Zero order

First order

Second order

Volatile

Tendency of a substance to vaporize (turn into a gas). More volatile, easier to become a gas.

Enthalpy

Number of configurations. Delta S.

Gas is always highest in enthalpy.

Ionic Bond

Most powerful bond.

When one atom wants to give an electron and one atom wants to take an electron.

Ex:

Want to give- Alkiane Metals (1st row on table, Li-Cs)

Want to take- Halogens (2nd to last row on table, F-I)

Covalent Bond

Both atoms want bonds to electrons. Usually made of two similar electronegative elements.

Bond Energy

Energy between atoms= Electronegativity in atom.

Breaking bonds= (-)

Making bonds= (+)

Based on charge strength:

More charge = More strength

More bonds= More charge

MORE STRENGTH= LESS BOND LENGTH

Bond Length

Distance between atoms. As you shorten the distance between the atoms, attraction increases.

MORE BOND LENGTH= LESS BOND STRENGTH

Repulsion

When atoms get really close, repulsion occurs and pushes atoms apart.

Energy graph

Min of graph represents the highest amount of energy.

Bond energy absorbed when bond breaks (+) = Bond energy released when bind forms (-).

Bond Number

Number of bonds between two atoms in a molecule.

Increase the # of bonds, Decrease the bond length, Increase bond energy

Single bond= 1

Double bond=2

Triple bond= 3

Electronegativity

The power of an atom in a molecule to attract electrons to itself.

Electronegativity increases up and right on table.

Polar: particle charge occurs between to atoms with relatively close electonegativitiezs.

Nonpolar: Electrons are shared. No partial charges.

Dipole moment

Pull on atoms based on surrounding electonegativitiezs.

Intermolecular Forces

Forces between two molecules.

Strongest Ionic Bond

Hydrogen Bond

Dipole- Dipole

Weakest London Dispersion

Intramolecular Forces

Forces within a molecule.

London Dispersion Force

ANY Molecule.

More surface area= More options for dispersion forces.

Boiling point: Low

Dipole- Dipole Forces

Polar molecule, separation of charge.

There is electrostatic attraction and energy is needed to pull the molecules apart.

Boiling point: High, most likely liquid at room temp.

Hydrogen Bonding

Ability to bond to hydrogen.

Florine

Oxygen

Nitrogen

Boiling point: Higher because H-bonding is stronger version of Dipole- Dipole. More energy/heat is needed to pull Hydrogen-bonded molecules apart. Liquid at room temp.

Absorption

Electrons move from low energy state to high energy state. Electrons are absorbing energy for a period of time.

Emission

Electrons move from high energy state to low energy state.

Emits photons= Emits light

Energy of emitted photon= (initial energy level)-(final energy level)

Photon Energy

Ephoton= (Planks constant)(Speed of light)

---------------------------------------------

(Wavelength)

Planks constant= 6.626x10^-34

Speed Light= 2.997x10^8

Wavelength

Light emitted when electrons fall to a low energy state.

Wavelength= (Speed of light)

-----------------------

(Frequency)

Higher energy photons have a shorter wavelength.

Electromagnetic Spectrum

Visible Light:

Violet- 400- 420 nm

Indigo- 420- 440 nm

Blue- 440-490 nm

Green- 490-570 nm

Yellow- 570- 585 nm

Orange- 585- 620 nm

Red- 620- 780 nm

Violet---->Red = Decreasing Energy

Red<---- Violet= Increasing Wavelength

Residence

How many electron groups are around the atom.

Standard Cell Potential

DEF****

Delta V= Ecell= E reduced (Cathode) - E oxidized (Anode)

Ecell = Ecell(initial)- (Rt/nF)ln(Q)

More (+) E 1/2 life, more likely to proceed forward, Reduced.

More (-) E 1/2 life, more likely to proceed backwards, Oxidized. More (-) is best reducing agent.

Increasing temp means= Ecell> Ecell (initial)

Potential energy

Distance between molecules.

More distance is More Ep

Delta G (initial)

Change in Free Energy under standard conditions.

Under standard conditions--> Delta G=Delta G (initial)

Q

Q= [Products]

--------------- (Leave Solid)

[Reactants]

Increase Q, Delta G reaches equilibrium, still spontaneous, Voltage will Decrease.

Q=K, At equilibrium

Q>K, Too few reactants, goes towards reactants until equilibrium.

Q

Strong Acids

Strong Acid= Weak conjugate base

Stronger the acid the more likely to disassociate ions in water (solubility).

HClO4---(Perchloric acid)

HCl---(Hydrochloric acid)

HBr---(Hydrobromic acid)

HI---(Hydroiodic acid)

HNO3---(Nitric acid)

H2SO4---(Sulfuric acid)

HClO3---(Chloric acid)

Strong Bases

Strong Base= Weak Conjugate Acid

LiOH--- (Lithium hydroxide)

NaOH--- (Sodium hydroxide)

KOH--- (Potassium hydroxide)

Ca(OH)2--- (Lithium hydroxide)

LiOH--- (Lithium hydroxide)

LiOH--- (Lithium hydroxide)

Electromagnetic Radiation

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