The potential difference (ddp) of a battery is the electrical current produced from two electrodes through the phenomena of oxidation and reduction. We can also call ddp electromotive force (whose initials is emf) or potential variation (whose initials is ΔE).
The electrical voltage generated when electrons move from the electrode that undergoes oxidation towards the electrode that undergoes reduction is the ddp, which is always indicated by the unit Volts (symbol V).
The ddp voltage produced in a cell depends on the potential that the electrodes have. Every electrode has an ability to oxidize or reduce, so if it oxidizes, it is because its oxidation potential has surpassed that of the other electrode or vice versa.
? ddp calculation
For calculate ddp of a battery, it is necessary that we know the reduction or oxidation potentials of each of the electrodes:
ΔE = Emajor reduction - ANDminor reduction
or
ΔE = Egreater oxidation - ANDminor oxidation
The reduction potential of an electrode has the same value as its oxidation potential, but with the opposite sign.
? Examples of ddp calculation
(ESCS-DF) Cells and batteries are devices in which electrical current is produced through an oxidation-reduction reaction. Knowing the standard electrode reduction potentials:
Ass2+ + 2 and– Cu E° = + 0.34 V
Ag+ + and– Ag E° = + 0.80 V
The standard potential difference (ΔE°) of the Cu | Ass2+ (1M) || Ag+ (1M) | Ag is equal to:
a) 0.12 V b) 0.46 V c) 1.12 V d) 1.14 V e) 1.26 V
Resolution:
ANDmajor reduction = + 0.80V
ANDminor reduction = + 0.34V
ΔE = Emajor reduction - ANDminor reduction
ΔE = 0.80 - 0.34
ΔE = 0.46V.
(UESPI) An important contribution of Eletroquímica to our day to day are the portable batteries used in electronic equipment. These batteries are electrochemical cells in which the current - flow of electrons through the circuit - is produced by a spontaneous chemical reaction or to force the processing of a reaction that does not spontaneous. In this sense, a galvanic cell uses oxidoreduction reactions to convert chemical energy into electrical energy. Determine the voltage produced by a galvanic cell in which the reaction takes place
Ag+(here) + Cr2+(here) → Ag(s) + Cr3+(here),
and where the ionic concentrations are equal to 1 mol. L–1. Standard oxidation potential data at 25 °C:
Cr2+(here) → and– + Cr3+(here) ΔE = -0.41V
Ag(s) → and– + Ag+(here) ΔE = - 0.80V
a) –0.39 V b) +0.39 V c) –1.21 V d) +1.21 V e) +1.61 V
Resolution:
ANDgreater oxidation = + 0.80V
ANDminor oxidation = -0.80V
ΔE = Egreater oxidation - ANDminor oxidation
ΔE = -0.41 - (-0.80)
ΔE = -0.41 + 0.80
ΔE = 0.39V.
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/quimica/o-que-e-ddp-de-uma-pilha.htm