Electrochem Flashcards
standard hydrogen electrode
inert platinum electrode coated with finely divided Pt
immersed in 1 moldm-3 of H+ ions
H2 gas kept at 1 bar
temp kept at 25*C or 298K
standard electrode potential
potential difference between a standard hydrogen electrode and a half cell under standard conditions at 1 moldm-3, 25*C and 1 bar
galvanic cell
anode: oxidation, electrons released, negative terminal
cathode: reduction, electrons absorbed, positive terminal
standard cell potential
emf of a galvanic cell which consists of 2 half cells connected under standard conditions of 25*C, 1 bar, 1moldm-3 concentration. the Ecell value is the difference between the 2 standard electrode potentials
formula for E cell
E cathode - E anode
positive: spontaneous
formula for G cell
-nFE cell
limitations of galvanic cell
some reactions have high Ea, not kinetically favourable
actual conditons are not standard condtions
Electrolysis definition
a process in which a current is passed through the elctrolyte to decompose it
electrolytic cell
anode: positive terminal, connected to positive side of battery
cathode: negative terminal
electrons migrate to cathode
considering E of competing species
As A has less positive E than B, A is more readily oxidised and hence will be preferrably discharged at the anode
if concentration of A+ is higher
the increased [A+] in concentrated solution increased the tendency for reduction of [A], making the E of [A] half cell to be more positive than B
But it does not shift to such an extent to be more/less than…
It shifts to such an extent to be more positive than…
Faradays first law of electrolysis
the mass of a substance liberated at an electrode during electrolysis is directly proportional to the quantity of electricity passing through the electrolyte
Faradays second law of electrolysis
the number of Faradays required to discharge 1 mole of an ion at an electrode equals the amount of charges on the ion
