Electrochemistry Flashcards
electromotive force
Ecell = Ecathode - Eanode
difference between standard production potential of the reaction at the anode and the cathode
work that is done per unit of charge or joules of work per coulomb of charge
standard reduction potential
potential (in volts) required to reduce the compound
the more negative something is, the less likely it will be reduced
electrolytic cells
standard reduction potential is negative
non spontaneous reaction
charging –> external potential is applied to force oxidation-reduction reaction
galvanic cell
electrochemical cell that converts chemical energy into electrical energy via an oxidation reduction reaction
occurs spontaneously
Ecell = +
concentration cell
type of galvanic cell in which ions diffuse across a membrane and create a potential
standard reduction potential is postive
fuel cell
type of galvanic cell whose reactants are continuously supplied at the anode and cathode, and whose products are removed from the system
Ecell = +
electroplating
deposition of solids from electrolysis
involves reduction of a metal ion to a metal solid at the cathode of an electrolytic cell
calculating electroplating
It/nF
IT is Not Fun
Q=IT
charge in Coulombs - current (amps) x time (seconds)
n = moles F= Farday's constant = 96,500C/mole e-
To charge a battery what must the external potential be?
a greater voltage than what is produced by a discharging battery
this is because circuits have an internal resistance that will deplete a portion of the applied voltage so the reverse reaction will require more of an applied potential to drive the reaction in a non-spontaneous direction
What charge does the applied potential produce?
a positive charge because the potential must overcome the negative potential of the reverse reaction
when the products of the concentration of ions in a solution is equal to Ksp
equilibrium
dissolution and precipitate rates are equal
Why does a precipitate form?
when the concentration of ions is larger than the Ksp value
[Mg][OH]^2 > Ksp
therefore there is extra stuff that won’t be dissolved
what causes corrosion to occur more quickly?
metals in the presence of anions with which they form soluble salts will corrode more quickly than they will in pure water
solubility
based on number of moles that can dissolve in a given volume of solvent
Faraday’s constant
96,500 C/moles electrons
Gibbs free energy in galvanic cell equaiton
delta G = -nFE
F=faraday’s constant
e=cell potential = voltage
standard cell potential equation
E= - 0.0257lnK/n
or
E = 0.06logK/n
Nernst Equation
E = E0 + 0.0257lnQ/n
or
E = E0 + 0.06logQ/n
If the ETC is a spontaneous process, what must be true about the redox reactions within each of the four complexes?
The E’cell value increases as electrons are passed from one carrier to the next
because O2 is the final reducer, it needs to have a large E’cell (because the more positive the Ecell, the more the complex wants to accept electrons)
catabolism
breaking down biological fuel molecules like carbohydrates, lipids, and proteins into smaller molecules
oxidative process that releases energy –> becomes reduced itself
ex: NAD+–>NADH
NADH is a product of catabolic oxidation
electron transduction
energy travels from the passing of electrons from donor (NADH/FADH2) to acceptors (ETC –> O2)
anabolism
requires energy to build more complex things
reduces things to become oxidized itself
reference electrode
has a known electric potential and standard concentration of reacting species
concentration cell
both electrodes contain the same chemical species
Polarization
unequal distribution of electron density in polarized molecules that induces a dipole
