Question

Which Nernst equation is true to find out the potential of non-standard electrochemical cell from the following? $Fe(s)|F{e}^{2+}(aqXM)||I^{-}(aq)I_2(s)Pt$

• A. $E_{cell}=E_{cell}^{\text{o}}-\frac{0.592}{n}{\log }_{10}[F{e}^{2+}]{[I^{-}]}^2$
• B. $E_{cell}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{\log }_{10}[F{e}^{2+}]{[I^{-}]}^2$
• C. $E_{cell}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{\log }_{10}[F{e}^{2+}][I^{-}]$
• D. $E_{cell}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{\log }_{10}\frac{[F{e}^{2+}]{[I^{-}]}^2}{[Fe][I_2]}$

Answer 1

Answer: (B)

Cell reaction of a given cell is $\begin{array}{rl}& \underline{\begin{array}{rl}& Fe\to F{e}^{2+}+2e^{-}\\ & I_2+2e^{-}\to 2I^{-}\end{array}}\\ & Fe+I_2\to F{e}^{2+}+2I^{-}\end{array}$ According to Nernst equation $E_{cell}=E_{cell}^{\text{o}}+\frac{0.0592}{n}{\log }_{10}\frac{[Fe][I_2]}{[F{e}^{2+}]{[I^{-}]}^2}$ $[Fe]=[I_2]=1$ $E_{cell}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{\log }_{10}[F{e}^{2+}]{[I^{-}]}^2$