Electrode Potential
half cell half of an electrochemical cell
constructed of a metal electrodedipped in its ions or a platinum
electrode with 2 aqueous ions
e g electrode Fe solution Felt or Fe3 7Feltrag t Ze Feis
above reaction in equilibriumonlyoccurs when connected to
another half cell
if we have a half cell with 2 aqueousions we must use an inert but
electricallyeconductive electrode platinum Pt is is most commonly used
g Fe3teag te I Felt ag
an electrochemical cell is created byjoining2different half cells togethe
half cells are joined by a wire voltmeter and a salt bridge
one half cell undergoes reduction and the other oxidation REDOX
emf E cell potentialdifference between the 2 half cells
measured using the voltmeter
electrons flow from a more reactive metal to a less reactive one
salt bridge is filter paper with saturated knoz solution allows free ion
to move through it which balances the charge
each half cell has an electrode potential CEO value
measured in volts
tell us how easily the half cell givesup electrons oxidised
determing which half cell is undergoing reduction and which is oxidised
Rule to remember
NO Problem
the most Negative half cell will undergo Oxidation
the most Positive half cell will undergo Reduction
equations are alwaysgiven in the reduction form with e on the left
flip the equation for oxidation beforeforming an overall equation
ensure no of e in both equations are equal beforecombining the
e g 2 n't ca g 2e E Zn s EQ
cult cag z e e cues Eo 8 39 most negative oxidation
overall equation
zncszzznztcag.it2e Y't
cultcage Ze TCU s bridge
2h15 cuzteag tze zenit cues tze
2h s CUZteag E Zn at CU S z nite Cult
Standard Hydrogen Electrode SHE
used as a reference to measure standard electrode potentials IET
EOof half cells can't be measured on their own we can measure them
against a reference half cell called a standard hydrogenelectrode SHE
SHE has E which equals 0.00 v
EO values are affectedbyconcentrationpressure and temperature
in order to compare them we require standard conditions
Temperature at 298k for H2 g V
Pressure at lookPa Cu
concentrations of ions at im old m 3 H
NOTE to get mold m 3 of Ht ions
we need I mold m 3 of HCl but 0.5 mold m 3 of
H2504 for standard Hydrogen electrode t cult
electrochemical series
list of half cell reactions and their standard electrode potentials
oxidisingagents they are reduced gain electrons found on the tee
side of half equations in electrochemicalseries higher EQ stronger
oxidising agent sohighertendency togain electrons moreeasilyreduced
reducingagents they are oxidisedfoundonrightsideof half equations in
to
electrochemical series strongerreducingagent highertendency lose
electrons
half cell half of an electrochemical cell
constructed of a metal electrodedipped in its ions or a platinum
electrode with 2 aqueous ions
e g electrode Fe solution Felt or Fe3 7Feltrag t Ze Feis
above reaction in equilibriumonlyoccurs when connected to
another half cell
if we have a half cell with 2 aqueousions we must use an inert but
electricallyeconductive electrode platinum Pt is is most commonly used
g Fe3teag te I Felt ag
an electrochemical cell is created byjoining2different half cells togethe
half cells are joined by a wire voltmeter and a salt bridge
one half cell undergoes reduction and the other oxidation REDOX
emf E cell potentialdifference between the 2 half cells
measured using the voltmeter
electrons flow from a more reactive metal to a less reactive one
salt bridge is filter paper with saturated knoz solution allows free ion
to move through it which balances the charge
each half cell has an electrode potential CEO value
measured in volts
tell us how easily the half cell givesup electrons oxidised
determing which half cell is undergoing reduction and which is oxidised
Rule to remember
NO Problem
the most Negative half cell will undergo Oxidation
the most Positive half cell will undergo Reduction
equations are alwaysgiven in the reduction form with e on the left
flip the equation for oxidation beforeforming an overall equation
ensure no of e in both equations are equal beforecombining the
e g 2 n't ca g 2e E Zn s EQ
cult cag z e e cues Eo 8 39 most negative oxidation
overall equation
zncszzznztcag.it2e Y't
cultcage Ze TCU s bridge
2h15 cuzteag tze zenit cues tze
2h s CUZteag E Zn at CU S z nite Cult
Standard Hydrogen Electrode SHE
used as a reference to measure standard electrode potentials IET
EOof half cells can't be measured on their own we can measure them
against a reference half cell called a standard hydrogenelectrode SHE
SHE has E which equals 0.00 v
EO values are affectedbyconcentrationpressure and temperature
in order to compare them we require standard conditions
Temperature at 298k for H2 g V
Pressure at lookPa Cu
concentrations of ions at im old m 3 H
NOTE to get mold m 3 of Ht ions
we need I mold m 3 of HCl but 0.5 mold m 3 of
H2504 for standard Hydrogen electrode t cult
electrochemical series
list of half cell reactions and their standard electrode potentials
oxidisingagents they are reduced gain electrons found on the tee
side of half equations in electrochemicalseries higher EQ stronger
oxidising agent sohighertendency togain electrons moreeasilyreduced
reducingagents they are oxidisedfoundonrightsideof half equations in
to
electrochemical series strongerreducingagent highertendency lose
electrons
