electrochemistry Flashcards
electrochemistry is the interconversion of
chemical and electrical energy
Spontaneous reactions can produce electricity and power
power a nonspontaneous reaction to occur
Oxidation means loss of
electrons
Reduction is the gain of
electrons
whats oil rig
Oxidation Is Loss ELECTRONS
Reduction Is gain ELECTRONS
redox reactions involve movement of _______ from one _______ to another
electrons
reagent
WHAT DOES O2 FREQUENTLY ACT AS
an oxidizing agent
Steps for balancing reagents
- write down two half-reactions containin
- balance atoms and charges
- electrons should cancel out
- add the balanced half reactions
- check both charges balance
Two types of voltaic cells
voltaic cell
electrolytic cell
Voltaic/galvantic cells are
spontaneous chemical reaction generates an electric current
electrolytic cells are….
and they have to be ……..
non-spontaneous reactions are driven by electric current
what things typically contains voltaic/galvantic cells
batteries
does Voltaic cell system do work on surrounding or does surrounding do work on it? how>
yes it does work on the surroundings
by converting high energy in reactants in cell to lower energy products
does electrolytic cell system do work on surrounding or does surrounding do work on it? how?
the surrounding does work on the electrolytic cell system
Lower energy reactants are converted to higher energy products in ce;;
Voltaic cells use _____ reactions (G ___ 0) to do generate electrical energy
spontaneous
G < 0
salt in salt bridge go towards
reduction
Electric current is
flow of electrons
electrons only flow if the ____. force is large enough
driving
Anode is the electrode where
oxidation happens
cathode is the electode where
reduction happens
red cat means
reduction is cathode
electrodes are _____ strips connected by an _____ conducting wire
metal
electrically
salt bridge: _ shaped tube contains a ___ ____________ solution of an ________ electrolyte
U
gel permeated
inert
What does salt bridge do
keeps half cells electrically neutral as ions flow in and out
Voltaic cell notation
anode
cathode
Anodes are on the left
cathodes on the right
Voltaic cell notation
the order of written half cell
written in same order that would appear in their own half cell rxns
voltaic cell notation
double line
means that half-cells are physically separated
voltaic cell notation
if needed concentrations..
if not given concentration
it would be in brackets
assume 1M
voltaic cell notation
direction of electron flow
——–>
voltaic cell notation
comma
shows components taht are in the same phase
voltaic cell notation
“graphite”
shows any inactive (inert) electrode
Differing abilities of the metals to gain electrons gives rise to a ____ _____. Known as __________ ____ (EMF) or cell potential
voltage drop
electromotive force
multimeter measures
voltage
Cell potential (Ecell) is the
difference in electrical potential between two electrodes
if Ecell > 0 for VOLTAIC CELLS
spontaneous
if Ecell < 0 for ELECTROLYTIC CELLS
non spontaneous
Ecell bigger general formula
Eoxidation + Ereduction
Are half cell potentials multiplied
no
Lower Ecell voltage is always
flipped sign
whats S.H.E stand for. what is it
standard hydrogen electrode
reference point
potentials are determined experimentally from the _______ in potential
difference
S.H.E arbitraty value of
0.00V
how is Ecell related to thermodynamic property
negative
way to determine equilibrium constant for redox
-nFEcell = ΔG° = -RTlnK
ECELL (draw triagnle)=
(RT/NF) x lnK
K from equilibrium concentration/ partial pressures
k = [C]ᶜ[D]ᵈ/ [A]ᵃ[B]ᵇ
K FOR STANDARD STATE THEROMCEMIAL
lnk = -ΔG°/RT
K for standard state electrochemical data IF EQUILIBRIUM INVOLVED REDOX REACTION
also what else need to remember?
lnK = nFE°cell/RT
account for the amount of charge transferred
Nernst equation
E= E° - RT/nF lnQ
cell potential depends on relative …
concentrations of reactants and products
When Q < 1, ln Q < 0, so E cell…..
when Q = 1, ln Q = 1, so E cell…..
When Q > 1, ln Q > 0, so E cell….
E cell > E°
E cell = E°
E cell < E°
As cell is operated, concentrations of reactants will decrease and products will increase, but overall, this consequence of cell potential is
the overall cell potenetial decrease over time
what do concentration cells capture
electrical energy from concentration difference when
E cell =. (cathode and anote way_
E cell = E cathode - E anode
a concentration cell _____ the effect of concentration differences.
EXPLOITS
E cell > 0 as long as the half-cell concentrations are
different
Once concentrations in concentration cells equalize, ____ = _____ and current stops ______
Ecell = 0
flowing
Galvanization is
coating of iron with zinc
at 25C, what altnerate form can i use to find equilibrium constant
logK = nEcell/0.0592
