Chemistry Electrochemistry Flashcards
___ is the study of the relationships between chemical reactions and electrical energy
electrochemistry
___ include spontaneous reactions that produce electrical energy and nonspontaneous reactions that use electrical energy to produce a chemical change
electrochemical reactions
There are two types of ___: galvanic cells (also known as voltaic cells) and electrolytic cells
electrochemical cells
Spontaneous reactions occur in ___, and nonspontaneous reactions occur in electrolytic cells
galvanic
Both reaction types contain electrical conductors known as electrodes, where ___ and reduction occur
oxidation
For all electrochemical cells, the ___ where oxidation occurs is called the anode, and the electrode where reduction occurs is called the cathode
electrode
___ in an electrochemical cell: AN OX and a RED CAT. The ANode is the site of OXidation; REDuction occurs at the CAThode
electrodes
A redox reaction occurring in a ___ has a negative delta G and is therefore a spontaneous reaction
galvanic cell
The ___ from galvanic cell reactions is harnessed by placing the oxidation and reduction half-reactions in separate containers called half-cells
energy
The half cells are then connected by an apparatus that allows the flow of electrons between the ___, creating a circuit
half-cells
A salt bridge contains an inert electrolyte, usually KCL or NH4NO3 whose ions will not react directly with the ___ or the ions in solution
electrodes
The inert ions flow from the ___ toward the anode to balance the new ions being created, and the inert cations K+ flow toward the cathode to balance the Cu2+ being deposited onto the cathode. This flow depletes the salt bridge and, along with the finite quantity of Cu2+ in the solution, accounts for the relatively short lifetime of the cell. Note that the cations from the salt bridge flow to the cathode, and the anions flow to the anode; this is where the electrodes get their names from
salt bridge
The following rules are used in constructing a ___:
1. The reactants and products are always listed from left to right in the form:
anode | anode solution || cathode solution| cathode
2. A single vertical line indicates a phase boundary
3. A double vertical line indicates the presence of a salt bridge or some other type of barrier
cell diagram
A ___ occurring in an electrolytic cell has a positive delta G and is therefore nonspontaneous
redox reaction
In electrolysis, ___ is required to induce reaction
electrical energy
The anode of an electrolytic cell is considered ___ because it is attached to the positive pole of the battery
positive
The ___ of a galvanic cell, on the other hand is considered negative because the spontaneous oxidation reaction that takes place at the galvanic cell’s anode is the original source of that cell’s negative charge (is the source of the electrons
anode
Oxidation always takes place at the anode in both types of cells, reduction always takes place at the cathode in both types of cells, and electrons always flow through the wire from the ___ to the cathode
anode
___ flow in an electrochemical cell: FAT CAT Electrons flor From Anode To CAThode in all types of electrochemical cells
electron
In a ___, charge is spontaneously created as electrons are released by the oxidizing species at the anode. Since this is the source of electrons, the anode of a galvanic cell is considered the negative electrode
galvanic cell
The ANode of galvaNic cell is ___ Negative
always
In an electrolytic cell, ___ are forced through the cathode, where they encounter the oxidizing agent
electrons
The cathode is providing electrons, and thus the cathode of an electrolytic cell is considered the ___ electrode
negative
Like in any cell, the ___ attracts cations
cathode
The positively charged ___ cations (i.e., those that are protonated at the pH of of the solution) will migrate toward the cathode; negatively charged amino acid anions (i.e., those that are deprotonated at the solution pH) migrate instead toward the anode
amino acid
The ___ carried by one mole of electrons can be calculated by multiplying the electron charge (1.6E-19) by Avogrado’s number:
(1.6E-19)(6.022E23)=96,487 C/mol electrons
charge
96487 C/ mol electrons is known as ___ constant
Faraday’s
i x t = n x F
i = current in amperes, t = time in seconds, n = number of moles of ___, and F = the Faraday constant
electrons
The species in a redox reaction that will be oxidized or reduced can be determined from the ___ of each species, defined as the tendency of a species to acquire electrons and be reduced
reduction potential
Each chemical species has its own intrinsic ___ potential, the more positive the potential, the greater the tendency to be reduced
reduction
A ___ (E degree) means a greater tendency for reduction to occur, while a lower E degree means a greater tendency for oxidation to occur
higher standard reduction potential
When two ___ occur in the same system, only one can be a reduction; the half-reaction with the lower reduction potential will occur in reverse as an oxidation
half-reactions
Standard reduction potentials are also used to calculate the ___ (emf or E degree sub cell) of a reaction, the difference in potential between two half cells
standard electromotive force
The E degree sub cell of a reaction is determined by adding the standard reduction potential of the reduced ___ and the standard oxidation potential of the oxidized species
species
___ = E degree sub red + E degree sub ox
E degree sub cell
The standard E degree sub cell of a galvanic cell is ___, while the standard E degree sub cell of an electrolytic cell is negative
positive
The ___ for determining the spontaneity of a reaction is delta G, Gibbs free energy, a measure of the maximum amount of useful work produced by a chemical reaction
thermodynamic criterion
In an electrochemical cell, the work done is dependent on the number of coulombs and the energy available. Thus when standard conditions (25 degrees Celsius, 1 atm pressure, and all solutions at 1 M concentration) are present, delta G and E sub cell are related as follows:
delta G = -nFEcell
where n is the number of ___ of electrons exchanged, and F is the Faraday constant, 10^5 coulombs per mole
Keep in mind that if the Faraday constant is expressed in coulombs (J/V), delta G must be expressed in J, not kJ
moles
A ___ has a negative delta G and a positive E sub cell, whereas an electrolytic cell has a positive delta G and a negative E sub cell
galvanic cell
delta G = -RTlnK sub eq
This relates delta G to K sub eq, When K sub eq >1, products are favored over reactants, the forward ___ is spontaneous, and delta G < 0. When K sub eq < 1, reactants are favored, the reverse reaction is preferred, and delta G > 0.
Combining the different equations for delta G gives:
nFEdegree sub cell = RTlnK sub eq
This relationship shows that when K sub eq > 1, ln K sub eq > 0, and E degree sub cell is positive; thus, the reaction goes forward. When K sub eq < 1, ln K sub eq < 0, and E degree sub cell is negative; thus, the reaction goes in the reverse direction
reaction
Nernst equation:
E sub cell = E degree sub cell - (RT/nF)(lnQ)
Q is the reaction ___ for a given reaction and gives the concentration of reactants and products when the reaction is not at equilibrium
quotient
When:
aA + bB yields cC + dD
the reaction ___ would be:
Q = ([C]^c[D]^d)/([A]^a[B]^b)
This allows the actual E sub cell to be determined based on the E degree sub cell and reagent concentrations
Note that the Nernst equation can be rewritten as
E cell = E degree sub cell - (RT/nF)(lnQ) = (RT/nF)(lnK sub eq)-(RT/nF)(lnQ)
If Q = 1, as under standard conditions, when all concentrations are 1 M, then lnQ = 0, and the entire last term of the equation disappears
quotient
