Question

The standard electrode potential ${\text{E}}{{^\circ }_{{{\text{I}}_{\text{2}}}{\text{/r}}}}{\text{,E}}{{^\circ }_{{\text{B}}{{\text{r}}^{\text{ - }}}{\text{/B}}{{\text{r}}_{\text{2}}}}}{\text{ and E}}{{^\circ }_{{\text{Fe/F}}{{\text{e}}^{{\text{ + 2}}}}}}$ are respectively ${\text{ + 0}}{\text{.54V, - 1}}{\text{.09V and 0}}{\text{.44V}}$. On the basis of the above data which of the following processes is non spontaneous?

Answer 1

The individual potential of electrodes defined at one atm pressure and one mole per liter concentration is known as standard electrode potential. The measure for the process to define its spontaneity is known as Gibbs free energy.

Complete step by step answer:
Standard electrode potential is defined as the individual potential of an electrode at some standard conditions. The standard conditions to define the standard electrode potential are that the concentration of ions should be one mole per $d{m^3}$ and the pressure should be one (atm) atmospheric pressure.
The process which releases energy and moves towards the stable state which has lower energy is known as spontaneous process and the process with opposite functioning to it is known as non spontaneous process. The spontaneity of thermodynamic processes is determined by the Gibbs free energy. If the Gibbs free energy i.e. $\Delta G$ is negative ($\Delta G < 0$) then the process is spontaneous and if Gibbs free energy has positive ($\Delta G > 0$) value then it is non spontaneous.
In thermodynamics we have a unique relation between Gibbs free energy, electromotive force and the number of electrons involved in the reaction. The relation is as follows:
$\Delta G = - nF{E_{cell}}$
$\Delta G$ is Gibbs free energy, $n$ is the number of moles of electrons, $F$ (${\text{1Faraday = 96500coulombs}}$) and ${E_{cell}}$ is electromotive force measured in volts.
So from this formula we can see that if ${E_{cell}}$ is positive then $\Delta G$ is positive, hence they are opposite in sign.
The values of standard electrode potentials provided to us are: ${\text{ + 0}}{\text{.54V, - 1}}{\text{.09V and 0}}{\text{.44V}}$
So, ${\text{ - 1}}{\text{.09V}}$ is negative electromotive force, therefore the Gibbs free energy will be positive and hence the overall process will be non spontaneous.
The process included related to these emf values is as follows:
$B{r_2} + 2I \to 2Br + {I_2}$

Note: The constant defined in the fields of chemistry and physics by Michael Faraday which represents the magnitude of electric charge per mole of electrons is known as Faraday’s constant. It is represented as $'F'$ and the approximate value of this constant is ${\text{96500C}}$ .