The standard reduction potentials for the and half-cells are and , respectively. Which of the follow — Electrochemistry Chemistry Question
Question
The standard reduction potentials for the $Fe^{3+}/Fe^{2+}$ and $I_3^-/I^-$ half-cells are $+0.77\text{ V}$ and $+0.54\text{ V}$, respectively. Which of the following statements are TRUE regarding the chemical reaction $2Fe^{3+}(aq) + 3I^-(aq) \rightleftharpoons 2Fe^{2+}(aq) + I_3^-(aq)$?
💡 Solution & Explanation
The target redox reaction involves the reduction of $Fe^{3+}$ to $Fe^{2+}$ ($E^\circ = 0.77\text{ V}$) and the oxidation of $I^-$ to $I_3^-$ (reverse of reduction, so we subtract $0.54\text{ V}$). The standard cell potential $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 0.77 - 0.54 = +0.23\text{ V}$. Because $E^\circ_{cell} > 0$, the reaction is spontaneous ($\Delta G^\circ < 0$). Iodide ($I^-$) loses electrons to become oxidized, thus acting as the reducing agent.