Gen Chem: Final Exam

First Law of Thermodynamics

the internal energy of a system changes through heat exchange with the surroundings or work on or by the system

enthalpy

the heat flow for a process at constant pressure

state function

its value only depends only on the state of a system, and not the path taken to reach that state

exothermic

delta H is less than 0; thermal energy is transferred from the system to its surroundings

endothermic

delta H is greater than 0; thermal energy is transferred to the system from its surroundings

Hess’s Law

if a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes if the various steps

standard state

pure solid and liquid, pressure 1 atm (g), concentration 1 M (aq), and T = 298K

spontaneous process

process that takes place without a continuous input of energy from an external source

nonspontaneous

process that requires continual input of energy from an external source

entropy

measure of the disorder of the system

microstate

possible configuration or arrangement of matter and energy within a system

Second Law of Thermodynamics

all spontaneous processes involve an increase in the entropy of the universe

Third Law of Thermodynamics

entropy of a perfect crystal at absolute zero (0K) is zero

standard entropy

entropy for one mole of a substance at 1 atm pressure

Gibbs free energy change

thermodynamic property defined in terms of system enthalpy and entropy

electrochemistry

the study of the interconversion of electrical and chemical energy

electricity

presence and flow of electrical charge

active electrodes

the anode and cathode materials participate in the reactions

inert electrode

the half-reaction does not contain an active electrode

standard hydrogen electrode (SHE)

the reference for all half-cell potential values with an assigned value of 0 V for the oxidation reaction H₂ (g) —> 2H⁺ + 2e^-

standard reduction potentials (SRP)

determined by the determination of the potential of a cell made up of a reduction reaction and the SHE

Chloralkali Process

aqueous sodium chloride can be electrolyzed to produce NaOH (aq) and Cl₂ (g)

Hall-Héroult process

a molten mixture of aluminum ore (bauxite, AL₂O₃) and cryolite (Na₃AlF₆) are electrolyzed at (>900^oC) to produce very pure aluminum metal

batteries

single or series of galvanic cells designed for use as a source of electrical power

primary cell

non-rechargeable battery, suitable for single use only

secondary cell

batter designed to allow recharging

fuel cell

galvanic cells that require a continuous feed of redox reactants

corrosion

degradation of metal via a natural electrochemical process; always oxidation

dispersion forces

fleeting, temporary dipoles resulting in weak electrostatic forces between molecules when very close together

instantaneous dipoles

result from constant motion of electrons in molecules and atoms

induced dipoles

result when an instantaneous dipole in one molecule or atom distorts the electrons in a neighboring atom or molecule

polarizability

measure of how easy or difficult it is for another electrostatic charge to distort a molecule’s charge distribution

hydrogen bonding

an unusually strong type of dipole-dipole attraction

what is the ranking of intermolecular forces?

hydrogen bonding > dipole-dipole > dispersion

cohesive forces

attraction between identical molecules of a substance

adhesive forces

attraction between different types of molecules

viscosity

the measure of a liquid’s resistance to flow

surface tension

the energy required to increase the area, or length of a liquids surface by a certain amount

capillary action

liquid flow within a porous material due to attraction of the liquid to the surface of the material and to other liquid molecules

vaporization

endo or exo?

liquid → vapor

endo

condensation

endo or exo?

vapor → liquid

exo

melting

endo or exo?

solid → liquid

endo

freezing

endo or exo?

liquid → solid

exo

sublimation

endo or exo?

solid → gas

endo

deposition

endo or exo?

gas → solid

exo

dynamic equilibrium

reciprocal process occur at the same rates

vapor pressure

the pressure exerted by a vapor in equilibrium with a liquid in a closed container at a given temperature

normal boiling point

the temperature at which the liquid boils when the pressure above the liquid is 1 atm

enthalpy of vaporization

endo or exo?

the energy required to vaporize one mole of a liquid substance

endo

enthalpy of fusion

endo or exo?

the energy required to melt one mole of a solid substance at a temperature

endo

enthalpy of sublimation

endo or exo?

the energy required to convert one mole of a solid substance directly to the gaseous state

endothermic

where are the phases located on a phase diagram?

1. left

2. right

3. bottom

1. solid

2. liquid

3. gas

triple point

the temperature and pressure at which solid, liquid, and vapor of a substance are all in equilibrium

critical point

the temperature and pressure above which a gas cannot be condensed into a liquid

supercritical fluid

the high density, low viscosity phase intermediate between liquid and gas

crystalline solid

solids in which atoms, ions, or molecules are arranged in a definite repeating pattern

amorphous solids

glassy or noncrystalline solids that lack an ordered internal structure

ionic solid

solid composed of cations and anions held together by strong electrostatic attractions

metallic solid

solid composed of metal atoms