Question

Calculate the E^ocell for: Fe(s) + Br₂(g) →   Fe²⁺(aq) +Br^-(aq) ; is this electrolytic or voltaic?

	A.	-1.52V ; voltaic
	B.	1.52V ; electrolytic
	C.	-1.52V ; electrolytic
	D.	1.52V ; voltaic

Answer 1

The standard electrode potential for Zn system is Zn²⁺ + 2e^- Zn ; E^o red = -0.7628 V ---(1)

The standard electrode potential for Cu system is Cu²⁺ + 2e^- Cu ; E^o red = +0.340 V ---(2)

Since the reduction potential of Zn system is less it undergoes oxidation at anode & Cu undergoes reduction at cathode.

The cell reaction is

The standard electrode potential for Fe system is Fe²⁺ + 2e^- ----> Fe ; E^o red = -0.44 V ---(1)

The standard electrode potential for Cu system is Br₂(aq) + 2e^- ----> 2Br-(aq) ; E^o red = +1.08 V ---(2)

Since the reduction potential of Fe system is less it undergoes oxidation at anode & Br undergoes reduction at cathode.

The cell reaction is Fe(s) + Br₂(g) →   Fe²⁺(aq) +Br^-(aq)

So standard potential of the cell , E^o = E^o_cathode - E^o_anode

                                                      = E^o_Br-/Br - E^o_Fe2+/Fe

                                                      = +1.08 - (-0.44) V

                                                     = +1.52 V

So standard potential of the cell , E^o = +1.52V

Since the voltage difference occurs due to the migration of electrons so it is electrolytic

Therefore option (B) is correct