CHEM 108: Extra - Electrochemistry and Nuclear Chemistry

electrochemistry

the branch of chemistry that examines the transformations between chemical and electrical energy

redox reactions

reactions in which a substance gains or loses electrons

oxidation

occurs when an atom’s oxidation state increases during a reaction (gain electrons)

reduction

occurs when an atom’s oxidation state decreases during a reaction (lose electrons)

reducing agent

reactant that reduces an element, contains the element that is oxidized

oxidizing agent

reactant that oxidizes an element, contains the element that is reduced ele

electrochemical cell

apparatus that converts chemical energy into electrical work or electrical work into chemical energy

cell diagram

symbols that show how the components of an electrochemical cell are connected

electrodes

surfaces for exchange of electrons

anode

electrode at which an oxidation occurs

cathode

electrode at which a reduction occurs

current

the number of electrons that flow through the system per second

unit for current

ampere

1 A

6.242e18 electrons per second

electrode surface area dictates

the number of electrons that can flow

larger batteries produce

larger currents

potential difference

difference in potential energy between reactants and products

electromotive force

amount of force pushing the electrons through the wire

cell potential

the difference in potential energy between the anode and the cathode in a voltaic cell

cell potential depends on

relative ease of reduction and oxidation

standard reduction potential

potential of a reduction in half-reaction in which all reactants/products are in standard states

standard cell potential

measure of how forcefully an electrochemical cell can pump electrons through an external circuit

electrical work

charge x potential difference

voltaic cell

electrochemical cell in which chemical energy is transformed into electrical energy by a spontaneous redox reaction

Ecell

cathode - anode

Standard Hydrogen Electrode (SHE)

given value of 0V, all half cell potentials are measured relative to SHE

positive cell voltages give

negative delta G values, spontaneous redox reactions

strongest oxidizing agents

largest E cell values

strongest reducing agent

most negative E cell value

free energy and Ecell formula

Faraday’s constant

96500 C

what kind of variable is Ecell?

intensive variable

what kind of variable is delta G?

extensive variable

concentration cells

it is possible to get a spontaneous reaction when the oxidation and reduction reactions are the same, as long as the electrolyte concentrations are different

direction of electrons flow in an electrode

less concentrated solution to a more concentrated solution

less concentrated solution

has the anode

more concentrated solution

has the anode

nernst equation

electrolysis

process in which electrical energy drives a nonspontaneous chemical reaction

electrolytic cell

device in which an external source of electrical energy does work on a chemical system, turning reactants into higher-energy products

nucleon

protons, neutrons

nuclide

any particular nucleus

atomic number (Z)

number of protons, nuclear charge

atomic mass (A)

number of protons and number of neutrons

isotopes

atoms whose nuclei have the same Z but different A

nuclear chemistry

the study of reactions that involve changes in the nuclei of atoms

radioactive decay

the spontaneous disintegration of unstable particles accompanied by the release of radiation

nuclear reaction

involves nuclei - mass number and atomic number must be balanced

alpha rays

positively charged

beta rays

negatively charged

gamma rays

neutral

antimatter

particles that are charge opposites of normal subatomic particles

annihilation

result of a collision of matter/antimatter particles

alpha emission

emission of helium nucleus - decrease atomic number by 2, decrease mass number by 4

gamma emission

emission of photon from nucleus

beta emission

emission of electron from the nucleus - increase atomic number by 1

positron emission

emission of positively-charged electron from a nucleus - decrease atomic number by 1

electron capture

reaction of proton and electron - atomic number decreases by 1

radioactive decay formula

magic numbers

numbers of nuclear particles in a completed shell of protons or neutrons

magic numbers for protons

2, 8, 20, 28, 50, and 82

magic numbers for neutrons

2, 8, 20, 28, 50, 82, and 126

belt of stability

region on a graph of the number of neutrons vs. number of protons that includes all stable nuclei

neutron rich

undergo beta decay

neutron poor

undergo positron decay or electron capture

lighter elements

fusion

heavier elements

fissionn

nuclear fusion

nuclear reaction in which sub-atomic particles or atomic nuclei collide and fuse together, forming more massive nuclei and releasing energy

energy released from the formation of a single helium nucleus

-3.955e-12 J

mass defect formula

mass of products - mass of reactants

binding energy

the energy release when nucleons combine to form a nucleus

EINSTEIN’S EQUATION

fus

fusion reactors

high-temperature reactions between deuterium and tritium

tokamak

high-temperature reactions produce an incandescent plasma which is contained by strong magnetic fields

nuclear fission

nuclear reaction in which a heavy nucleus splits into two lighter nuclei, accompanied by the release of one or more neutrons

chain reactions

a self-sustaining series of fission reactions in which neutrons released when nuclei split apart initiate additional fission events

critical mass

the minimum amount of fissionable material needed to sustain a chain reaction