Electrochemistry Flashcards
redox reaction
oxidation-reduction reaction
e-s transferred from one atom to another
oxidized = loses e-s
reduced = gains e-s
oxidation states
possible charge values that an atom may hold within a molecule
must add up to the charge on molecule or ion
oxidation state of 0
atoms in their elemental form
oxidation state of -1
fluorine
oxidation state of +1
hydrogen (except when bonded to a metal like NaH, then -1)
oxidation state of -2
oxygen (except when it is in a peroxide like H2O2, then -1)
reducing agent/reductant
compound giving electrons, oxidized
oxidizing agent/oxidant
compound accepting electrons, reduced
electric potential (E)
associated with any redox reaction because e-s are transferred
half reaction
each component of redox reaction
one possible potential for any given half reaction
reduction potentials
how half reactions are usually written
sign reversed for the oxidation potential
more positive - stronger oxidizing agents, easily reduced
more negative - stronger reducing agents, easily oxidized
standard hydrogen electrode half reaction
2H+ + 2e- –> H2
E = 0.00V
galvanic cell/voltaic cell
uses the electric potential between phases to generate a current of e-s from one phase to another in a conversion of chemical energy to electric energy
salt bridge
phase that is impermeable to e-s in a galvanic cell
ionic conductor carrying current in form of ions
terminals or galvanic cell
electronic conductors (metal wires) emf is electric potential difference between terminals
2 electrodes of galvanic cell
anode (-) and cathode (+) oxidation at anode reduction at cathode e-s flow to cathode current flows cathode --> anode
cell potential (E) / electromotive force (emf)
potential difference between the terminals )when they are not connected
positive cell potential indicates a ……. (with equation)
spontaneous reaction (delta)G = -nFE n = number of e-s transferred
(delta)G and (delta)G prime equation
(delta)G = (delta)G(prime) + RTln(Q) Q = the reaction quotient
equilibrium, (delta)G(prime) =
-RTln(K)
varies with temp
K= 1, (delta)G(prime) = 0
K >1, (delta)G(prime) 0
concentration cell
limited form of a galvanic cell with a reduction half reaction taking place in one half cell and the exact reverse of that half reaction in the other half cell
*type of galvanic cell, never at standard conditions
electrolytic cell
power source across the resistance of galvanic cell, force cell to run backwards
will have negative emf
cathode (-), anode (+)
reduction at cathode and oxidation at anode
used for metal plating and purifying metals
