MCAT Chemistry: Electrochemistry and nuclear chemistry

reduction

gaining electrons by forming bonds to less electronegative atoms (hydrogen) or losing bonds to more electronegative atoms (oxygen)

oxidation

loosing electrons by losing bonds to less electronegative atoms (hydrogen) and gainging bonds to more electronegative atoms (oxygen)

reduction

gaining electrons by forming bonds to less electronegative atoms (hydrogen) or losing bonds to more electronegative atoms (oxygen)

oxidation

loosing electrons by losing bonds to less electronegative atoms (hydrogen) and gainging bonds to more electronegative atoms (oxygen)

the oxidation state of any element in its standard state is

0

The sum of the oxidation states of the atoms in a molecule or ion

must equal the overall charge

oxidation state of group 1 metals

+1

oxidation state of group 2 metals

+2

oxidation state of fluorine

-1

oxidation state of hydrogen when bonded to a more electronegative atom

+1

oxidation state of hydrogen when bonded to a less electronegative atom

-1

except for peroxides, oxygen has an oxidation state of

-2

oxidation state of halogens

-1

oxygen family oxidation state

-2

reduction potentials

is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. In a reduction table, the given potential is for the reduction of the reactants

oxidation potentials

measure of the tendency of a chemical to lose electrons and be oxidized. In a reduction table, the products are being reduced and the oxidation potential is the negative of the reduction potential

Nonspontaneous reduction potentials are

negative

spontaneous reduction potentials are

positive

reducing agent

a compound that causes others to be reduced or gain electrons.

examples of reducing agents

H2, neutral metals, hydride reducing agents (LiAlH4, NaBH4)

examples of oxidizing agents

neutral nonmetals, oxides (MnO4-, CrO3)

strongest oxidizing agent

largest standard reduction potential

strongest reducing agent

most negative reduction potential

cell potential is not affected by

coefficients of the reaction

electrochemical cell notation

anode | electrolyte || electrolyte | cathode

cell potential is inversely proportional to

free energy

nerst equation

Delta G= -nFEcell

F = 96,500 C/mol

over time a quantity of electrons can be used to do work like

electroplating: coating an object with metal

all electrochemical cells consist of:

two conductive electrodes, an electrolyte bridging between the electrodes, a circuit to connect the electrodes (can have a resistor or power source)

galvanic or voltaic cell

part of a complete circuit with no external power source due to a positive cell potential. occurs when discharging a battery

electrolytic cell

part of a complete circuit with an external power source due to negative cell potential. occurs when recharging a battery

electroplating

An electrolytic process in which a metal ion is reduced and a solid metal is deposited on the surface of the cathode during battery discharge

Pitting

carrodes anode during discharging a battery

cathode in discharging battery

is reduced and is positive side of battery

Anode in a discharge battery

is oxidized and is the negative side of the battery

flow of electrons in a battery

anode to cathode ALWAYS; opposite current flow

anode in recharging battery

It is oxidized and is the positive side of the battery

cathode in recharging battery

is reduced and is the negative side of the battery

in an aqeous solution in an electrolytic cell, the cathode produces

H2

In an aqueous solution in an electrolytic cell, the anode produces

O2

rechargable batteries

car batteries/lead acid batteries

a cell in equilibrium has an actual cell potential equal to

0

actual cell potential equation

E = Estandard - (RT/nf)lnQ

n= number of electrons transferred

standard cell potential equation

Estandard = (RT/nF)lnK

n = number of electrons transferred

cerimetry

A redox titration method using ceric sulfate as the titrant.

half equivalence point of redox titration

Estandard of analyte (not titrant); analyte concentrations of reduced and oxidized form are in equilibrium

equivalence point of redox titration

occurs when all of the moles of reducing agent in the solution have been completely oxidized; actual cell potential

2x equivalence point of redox titration

E standard of the titrant; titrate concentration of two forms are in equilibrium

iodometry

a redox titration where the consumption of iodine indicates the endpoint

alpha decay

atom emits an alpha particle consisting of two protons and two neutrons. This decreases the atomic number by 2 and the mass number by 4. seen in atoms with large nuclei. least dangerous type of ionizing radiation

beta decay

An atom emits a beta particle consisting of -1 proton. This increases the atomic number by 1, seen in nuclei with high neutron/proton ratios. more dangerous

positron emission

An atom emits a positron consisting of one proton. This decreases the atomic number by 1, seen in nuclei with high proton/neutron ratios

electron capture

An inner orbital electron is captured by the nucleus of its own atom, causing a decrease in atomic number by 1. This occurs in nuclei with a high proton/neutron ratio

gamma decay

Nuclear decay that involves the release of gamma rays doesn't change the identity of the atom. accompanies nuclear reactions. most dangerous and most penetrable

half life

time it takes for a substance to decay to half of its original amount

to be considered safe, a radioactive species must

pass 10 half lives

nuclear reactions are always

exothermic

energy of decay equation

delta E = (bindng energy of parent) - (binding energy of daughter)

binding energy

The energy that holds the nucleus together; proportional to mass of the nucleus