Question

Use the standard half-cell potentials listed below to calculate the standard cell potential for the following reaction occurring in an electrochemical cell at 25�C. (The equation is balanced.)

3 Cl2(g) + 2 Fe(s) --> 6 Cl-(aq) + 2 Fe3+(aq)

Cl2(g) + 2 e- --> 2 Cl-(aq); E� = +1.36 V

Fe3+(aq) + 3 e- -->Fe(s); E� = -0.04 V

+1.32 V

-1.32 V

-1.40 V

+1.40 V

+4.16 V

Answer 1

Answer: + 1.40 V

Explanation:

The balanced chemical equation is:

$3Cl_2(g)+2Fe(s)\rightarrow 6Cl^-(aq)+2Fe^{3+}(aq)$

Here Fe undergoes oxidation by loss of electrons, thus act as anode. Chlorine undergoes reduction by gain of electrons and thus act as cathode.

$E^0=E^0_{cathode}- E^0_{anode}$

Where both $E^0$ are standard reduction potentials.

$E^0_{[Fe^{3+}/Fe]}=-0.04V$

$E^0_{[Cl_2/Cl^-]}=+1.36V$

$E^0=E^0_{[Cl_2/Cl^-]}- E^0_{[Fe^{3+}/Fe]}$

$E^0=+1.36-(-0.04V)=+1.40V$

The standard cell potential for the reaction is +1.40 V