Electrochemical Series - Study Corner

The Electrochemical Series

The electrochemical series is a list of reduction half reactions of common reduction-oxidation (redox) reactions and their corresponding standard potentials E°. The potentials were measured in Volts (V) relative to the standard hydrogen electrode (SHE), which has a potential of 0 V (highlighted in red). The standard potentials were measured under standard conditions, i.e., at a temperature of 298 K (25°C), a pressure of 1 atm, and a solution concentration of 1 M.

Potential values in following tables are from various sources available in public domains and school textbooks. They were then checked against the online textbook “Chemistry 2e” (https://openstax.org/details/books/chemistry-2e) and the “Physical Chemistry” textbook by P.W. Atkins (Physical Chemistry, P.W. Atkins, 6th Ed., Oxford University Press, New York). Potential values with higher precision were selected, and if values for a particular half-reaction are different from different sources, values from “Atkins’ Physical Chemistry” or “Chemistry 2e” were used, and denoted * for the former and ** for the latter.

1. Reduction Half Reaction (Half Cell) Standard Potentials in Decreasing Order of Oxidizing Strength

1.1. Standard potential range in descending order [+3.00 V … +1.229 V]

$\textbf{TABLE 1.1}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline H\textsubscript{4}XeO\textsubscript{6} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & XeO\textsubscript{3} + 3H\textsubscript{2}O & +3.0 \\ \hline F\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2F\textsuperscript{-} & +2.866 \\ \hline O\textsubscript{3} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & O\textsubscript{2} + H\textsubscript{2}O & +2.07 \\ \hline S\textsubscript{2}O\textsubscript{8}\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2SO\textsubscript{4}\textsuperscript{2-} & +2.05 \\ \hline Ag\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag\textsuperscript{+} & +1.98 \\ \hline Co\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co\textsuperscript{2+} & +1.81 \\ \hline H\textsubscript{2}O\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsubscript{2}O & +1.776 \\ \hline PbO\textsubscript{2} + SO\textsubscript{4}\textsuperscript{2-} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & PbSO\textsubscript{4} + 2H\textsubscript{2}O & +1.69 \\ \hline Au\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Au & +1.692 \\ \hline Pb\textsuperscript{4+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb\textsuperscript{2+} & +1.67 \\ \hline HClO\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HClO + H\textsubscript{2}O & +1.628 \\ \hline 2HClO + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsubscript{2} + 2H\textsubscript{2}O & +1.611 \\ \hline Ce\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ce\textsuperscript{3+} & +1.61 \\ \hline 2HBrO + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Br\textsubscript{2} + 2H\textsubscript{2}O & +1.60 \\ \hline NiO\textsubscript{2} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni\textsuperscript{2+} + 2H\textsubscript{2}O & +1.593 \\ \hline MnO\textsubscript{4}\textsuperscript{-} + 8H\textsuperscript{+} + 5e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn\textsuperscript{2+} + 4H\textsubscript{2}O & +1.507 \\ \hline Au\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Au & +1.498\\ \hline HClO + H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsuperscript{-} + H\textsubscript{2}O & +1.482 \\ \hline Cl\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Cl\textsuperscript{-} & +1.35827 \\ \hline Cr\textsubscript{2}O\textsubscript{7}\textsuperscript{2-} + 14H\textsuperscript{+} + 6e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Cr\textsuperscript{3+} + 7H\textsubscript{2}O & +1.33 \tiny{**(+1.232)} \\ \hline O\textsubscript{3} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & O\textsubscript{2} + 2OH\textsuperscript{-} & +1.24 \\ \hline ClO\textsubscript{4}\textsuperscript{-} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O & +1.23 \tiny{**(+1.189)} \\ \hline MnO\textsubscript{2} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn\textsuperscript{2+} + 2H\textsubscript{2}O & +1.23 \\ \hline O\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsubscript{2}O & +1.229 \\ \hline \end{tabular}$

1.2. Standard potential range in descending order [+1.21 V … +0.591 V]

$\textbf{TABLE 1.2}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline ClO\textsubscript{3}\textsuperscript{-} + 3H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HClO\textsubscript{2} + H\textsubscript{2}O & +1.21 \\ \hline Pt\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt & +1.20 \\ \hline Br\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Br\textsuperscript{-} & +1.0873 \\ \hline Pd\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pd & +0.987 \\ \hline Pu\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pu\textsuperscript{3+} & +0.97 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 4H\textsuperscript{+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO + 2H\textsubscript{2}O & +0.957 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 3H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HNO\textsubscript{2} + H\textsubscript{2}O & +0.92 \\ \hline 2Hg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg\textsubscript{2}\textsuperscript{2+} & +0.92 \\ \hline ClO\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsuperscript{-} + 2OH\textsuperscript{-} & +0.89 \\ \hline HO\textsubscript{2}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 3OH\textsuperscript{-} & +0.878 \\ \hline Hg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg & +0.851 \\ \hline Ag\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag & +0.7996 \\ \hline Hg\textsubscript{2}\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg & +0.7973 \\ \hline Fe\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe\textsuperscript{2+} & +0.771 \\ \hline BrO\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Br\textsuperscript{-} + 2OH\textsuperscript{-} & +0.76 \\ \hline NiS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni + S\textsuperscript{2-} & +0.76 \\ \hline [PtCl\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt + 4Cl\textsuperscript{-} & +0.755 \\ \hline O\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}O\textsubscript{2} & +0.695 \\ \hline [PtCl\textsubscript{6}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [PtCl\textsubscript{4}]\textsuperscript{2-} + 2Cl\textsuperscript{-} & +0.68 \\ \hline ClO\textsubscript{2}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsuperscript{-} + 2OH\textsuperscript{-} & +0.66 \\ \hline Hg\textsubscript{2}SO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg + SO\textsubscript{4}\textsuperscript{2-} & +0.62 \\ \hline MnO\textsubscript{4}\textsuperscript{2-} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{2} + 4OH\textsuperscript{-} & +0.60 \\ \hline TeO\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Te + 2H\textsubscript{2}O & +0.593 \\ \hline [PdCl\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pd + 4Cl\textsuperscript{-} & +0.591 \\ \hline \end{tabular}$

1.3. Standard potential range in descending order [+0.58 V … +0.142 V]

$\textbf{TABLE 1.3}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline [PtBr\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt + 4Br\textsuperscript{-} & +0.58 \\ \hline MnO\textsubscript{4}\textsuperscript{-} + 2H\textsubscript{2}O + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{2} + 4OH\textsuperscript{-} & +0.558 \\ \hline MnO\textsubscript{4}\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{4}\textsuperscript{2-} & +0.56 \\ \hline I\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2I\textsuperscript{-} & +0.5355 \\ \hline I\textsubscript{3}\textsuperscript{-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 3I\textsuperscript{-} & +0.53 \\ \hline Cu\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu & +0.521 \\ \hline NiO\textsubscript{2} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni(OH)\textsubscript{2} + 2OH\textsuperscript{-} & +0.49 \\ \hline NiOOH + H\textsubscript{2}O + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni(OH)\textsubscript{2} + OH\textsuperscript{-} & +0.49 \\ \hline Ag\textsubscript{2}CrO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Ag + CrO\textsubscript{4}\textsuperscript{2-} & +0.45 \\ \hline [RhCl\textsubscript{6}]\textsuperscript{3-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Rh + 6Cl\textsuperscript{-} & +0.44 \\ \hline O\textsubscript{2} + 2H\textsubscript{2}O + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 4OH\textsuperscript{-} & +0.401 \\ \hline [Ag(NH\textsubscript{3})\textsubscript{2}]\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2NH\textsubscript{3} & +0.373 \\ \hline ClO\textsubscript{4}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{3}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.36 \\ \hline [Fe(CN)\textsubscript{6}]\textsuperscript{3-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [Fe(CN)\textsubscript{6}]\textsuperscript{4-} & +0.36 \\ \hline Cu\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu & +0.34 \\ \hline ClO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{2}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.33 \\ \hline Hg\textsubscript{2}Cl\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg + 2Cl\textsuperscript{-} & +0.26808 \\ \hline AgCl + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + Cl\textsuperscript{-} & +0.22233 \\ \hline [HgBr\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + 4Br\textsuperscript{-} & +0.21 \\ \hline Bi\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Bi & +0.20 \\ \hline Co(OH)\textsubscript{3} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co(OH)\textsubscript{2} + OH\textsuperscript{-} & +0.17 \\ \hline Cu\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu\textsuperscript{+} & +0.153 \tiny{*(+0.16)}\\ \hline Sn\textsuperscript{4+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn\textsuperscript{2+} & +0.151 \\ \hline S + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}S & +0.142 \\ \hline \end{tabular}$

1.4. Standard potential range in descending order [+0.1 V … -0.399 V]

$\textbf{TABLE 1.4}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline [Co(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [Co(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{2+} & +0.1 \\ \hline NO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO\textsubscript{2}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.10 \\ \hline AgBr + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + Br\textsuperscript{-} & +0.0713 \\ \hline [Ag(S\textsubscript{2}O\textsubscript{3})\textsubscript{2}]\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2S\textsubscript{2}O\textsubscript{3}\textsuperscript{2-} & +0.017 \\ \hline Ti\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti\textsuperscript{3+} & 0.00 \\ \hline \textcolor{red}{2H\textsuperscript{+} + 2e\textsuperscript{-}} & $\textcolor{red}{\xrightarrow{\text{\hspace{15 pt}}}}$ & \textcolor{red}{H\textsubscript{2} } & \textcolor{red}{0.00} \\ \hline Fe\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe & -0.04 \\ \hline [HgI\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + 4I\textsuperscript{-} & -0.04 \\ \hline MnO\textsubscript{2} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn(OH)\textsubscript{2} + 2OH\textsuperscript{-} & -0.05 \\ \hline O\textsubscript{2} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HO\textsubscript{2}\textsuperscript{-} + OH\textsuperscript{-} & -0.08 \\ \hline Pb\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb & -0.1262 \\ \hline CrO\textsubscript{4}\textsuperscript{2-} + 4H\textsubscript{2}O + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr(OH)\textsubscript{3} + 5OH\textsuperscript{-} & -0.13 \\ \hline Sn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn & -0.1375 \\ \hline In\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In & -0.14 \\ \hline AgI + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + I\textsuperscript{-} & -0.15 \\ \hline [SnF\textsubscript{6}]\textsuperscript{2-} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn + 6F\textsuperscript{-} & -0.25 \\ \hline Ni\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni & -0.257 \\ \hline Co\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co & -0.28 \\ \hline [Ag(CN)\textsubscript{2}]\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2CN\textsuperscript{-} & -0.31 \\ \hline In\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In & -0.3382 \\ \hline Tl\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Tl & -0.34 \\ \hline PbSO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb + SO\textsubscript{4}\textsuperscript{2-} & -0.3505 \\ \hline Ti\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti\textsuperscript{2+} & -0.37 \\ \hline Se + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}Se & -0.399 \\ \hline \end{tabular}$

1.5. Standard potential range in descending order [-0.4030 V … -1.01 V]

$\textbf{TABLE 1.5}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline Cd\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd & -0.4030 \\ \hline In\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{+} & -0.40 \\ \hline Cr\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr\textsuperscript{2+} & -0.407 \\ \hline [Cu(CN)\textsubscript{2}]\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu + 2CN\textsuperscript{-} & -0.43 \\ \hline In\textsuperscript{3+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{+} & -0.44 \\ \hline Fe\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe & -0.447 \\ \hline S + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & S\textsuperscript{2-} & -0.47627 \\ \hline In\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{2+} & -0.49 \\ \hline [Ni(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni + 6NH\textsubscript{3} & -0.49 \\ \hline Ga\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ga & -0.549 \\ \hline [Cd(NH\textsubscript{3})\textsubscript{4}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 4NH\textsubscript{3} & -0.61 \\ \hline U\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & U\textsuperscript{3+} & -0.61 \\ \hline HgS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + S\textsuperscript{2-} & -0.70 \\ \hline Cr\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr & -0.744 \\ \hline Zn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn & -0.7618 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 2H\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO\textsubscript{2} + H\textsubscript{2}O & -0.80 \\ \hline Cd(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 2OH\textsuperscript{-} & -0.81 \\ \hline 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2} + 2OH\textsuperscript{-} & -0.8277 \\ \hline SiO\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 2H\textsubscript{2}O & -0.86 \\ \hline Fe(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe + 2OH\textsuperscript{-} & -0.88 \\ \hline Cr\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr & -0.913 \\ \hline SnS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn + S\textsuperscript{2-} & -0.94 \\ \hline PbS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb + S\textsuperscript{2-} & -0.95 \\ \hline FeS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe + S\textsuperscript{2-} & -1.01 \\ \hline \end{tabular}$

1.6. Standard potential range in descending order [-1.04 V … -2.07 V]

$\textbf{TABLE 1.6}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline [Zn(NH\textsubscript{3})\textsubscript{4}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4NH\textsubscript{3} & -1.04 \\ \hline [Cd(CN)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 4CN\textsuperscript{-} & -1.09 \\ \hline CdS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + S\textsuperscript{2-} & -1.17 \\ \hline Mn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn & -1.185 \\ \hline V\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & V & -1.19 \\ \hline [Zn(OH)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4OH\textsuperscript{-} & -1.199 \\ \hline [SiF\textsubscript{6}]\textsuperscript{2-} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 6F\textsuperscript{-} & -1.2 \\ \hline [Cr(OH)\textsubscript{4}]\textsuperscript{-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr + 4OH\textsuperscript{-} & -1.2 \\ \hline Zn(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 2OH\textsuperscript{-} & -1.245 \\ \hline [Zn(CN)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4CN\textsuperscript{-} & -1.26 \\ \hline ZnS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + S\textsuperscript{2-} & -1.40 \\ \hline Cr(OH)\textsubscript{3} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr + 3OH\textsuperscript{-} & -1.48 \\ \hline Zr\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zr & -1.539 \\ \hline Hf\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hf & -1.55 \\ \hline Ti\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti & -1.630 \\ \hline Al\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Al & -1.662 \\ \hline SiO\textsubscript{3}\textsuperscript{2-} + 3H\textsubscript{2}O + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 6OH\textsuperscript{-} & -1.697 \\ \hline U\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & U & -1.79 \\ \hline Be\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Be & -1.847 \\ \hline Np\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Np & -1.856 \\ \hline Th\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Th & -1.90 \\ \hline Pu\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pu & -2.03 \\ \hline Am\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Am & -2.048 \\ \hline [AlF\textsubscript{6}]\textsuperscript{3-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Al + 6F\textsuperscript{-} & -2.07 \\ \hline \end{tabular}$

1.7. Standard potential range in descending order [-2.09 V … -3.04 V]

$\textbf{TABLE 1.7}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline [Sc\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sc & -2.09 \\ \hline H\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsuperscript{-} & -2.23 \\ \hline Gd\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Gd & -2.279 \\ \hline Lu\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Lu & -2.28 \\ \hline Sm\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sm & -2.304 \\ \hline Nd\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Nd & -2.323 \\ \hline Y\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Y & -2.37 \\ \hline Mg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mg & -2.373 \\ \hline Ce\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ce & -2.483 \\ \hline La\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & La & -2.52 \\ \hline Na\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Na & -2.71 \\ \hline Ca\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ca & -2.868 \\ \hline Sr\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sr & -2.89 \\ \hline Ba\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ba & -2.912 \\ \hline Ra\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ra & -2.92 \\ \hline Cs\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cs & -2.92 \\ \hline Rb\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Rb & -2.93 \tiny{(** -2.98)} \\ \hline K\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & K & -2.931 \\ \hline Li\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Li & -3.04 \\ \hline \end{tabular}$

2. Reduction Half Reaction (Half Cell) Standard Potentials in Alphabetical Order

2.1. Oxidant list between Ag⁺ and Ca(OH)₂

$\textbf{TABLE 2.1}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline Ag\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag & +0.7996 \\ \hline Ag\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag\textsuperscript{+} & +1.98 \\ \hline AgBr + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + Br\textsuperscript{-} & +0.0713 \\ \hline AgCl + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + Cl\textsuperscript{-} & +0.22233 \\ \hline [Ag(CN)\textsubscript{2}]\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2CN\textsuperscript{-} & -0.31 \\ \hline Ag\textsubscript{2}CrO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Ag + CrO\textsubscript{4}\textsuperscript{2-} & +0.45 \\ \hline AgI + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + I\textsuperscript{-} & -0.15 \\ \hline [Ag(NH\textsubscript{3})\textsubscript{2}]\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2NH\textsubscript{3} & +0.373 \\ \hline [Ag(S\textsubscript{2}O\textsubscript{3})\textsubscript{2}]\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ag + 2S\textsubscript{2}O\textsubscript{3}\textsuperscript{2-} & +0.017 \\ \hline Al\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Al & -1.662 \\ \hline [AlF\textsubscript{6}]\textsuperscript{3-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Al + 6F\textsuperscript{-} & -2.07 \\ \hline Am\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Am & -2.048 \\ \hline Au\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Au & +1.692 \\ \hline Au\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Au & +1.498\\ \hline Ba\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ba & -2.912 \\ \hline Be\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Be & -1.847 \\ \hline Bi\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Bi & +0.20 \\ \hline Br\textsubscript{2}(\textit{aq}) + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Br\textsuperscript{-} & +1.0873 \\ \hline BrO\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Br\textsuperscript{-} + 2OH\textsuperscript{-} & +0.76 \\ \hline Ca\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ca & -2.868 \\ \hline Cd\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd & -0.4030 \\ \hline [Cd(CN)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 4CN\textsuperscript{-} & -1.09 \\ \hline [Cd(NH\textsubscript{3})\textsubscript{4}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 4NH\textsubscript{3} & -0.61 \\ \hline Cd(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + 2OH\textsuperscript{-} & -0.81 \\ \hline \end{tabular}$

2.2. Oxidant list between CdS and Cu²⁺

$\textbf{TABLE 2.2}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline CdS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cd + S\textsuperscript{2-} & -1.17 \\ \hline Ce\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ce & -2.483 \\ \hline Ce\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ce\textsuperscript{3+} & +1.61 \\ \hline Cl\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Cl\textsuperscript{-} & +1.35827 \\ \hline ClO\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsuperscript{-} + 2OH\textsuperscript{-} & +0.89 \\ \hline ClO\textsubscript{2}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsuperscript{-} + 2OH\textsuperscript{-} & +0.66 \\ \hline ClO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{2}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.33 \\ \hline ClO\textsubscript{3}\textsuperscript{-} + 3H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HClO\textsubscript{2} + H\textsubscript{2}O & +1.21 \\ \hline ClO\textsubscript{4}\textsuperscript{-} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O & +1.23 \tiny{**(+1.189)} \\ \hline ClO\textsubscript{4}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & ClO\textsubscript{3}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.36 \\ \hline Co\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co & -0.28 \\ \hline Co\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co\textsuperscript{2+} & +1.81 \\ \hline [Co(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [Co(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{2+} & +0.1 \\ \hline Co(OH)\textsubscript{3} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Co(OH)\textsubscript{2} + OH\textsuperscript{-} & +0.17 \\ \hline Cr\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr & -0.913 \\ \hline Cr\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr\textsuperscript{2+} & -0.407 \\ \hline Cr\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr & -0.744 \\ \hline CrO\textsubscript{4}\textsuperscript{2-} + 4H\textsubscript{2}O + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr(OH)\textsubscript{3} + 5OH\textsuperscript{-} & -0.13 \\ \hline Cr\textsubscript{2}O\textsubscript{7}\textsuperscript{2-} + 14H\textsuperscript{+} + 6e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Cr\textsuperscript{3+} + 7H\textsubscript{2}O & +1.33 \tiny{**(+1.232)} \\ \hline Cr(OH)\textsubscript{3} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr + 3OH\textsuperscript{-} & -1.48 \\ \hline [Cr(OH)\textsubscript{4}]\textsuperscript{-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cr + 4OH\textsuperscript{-} & -1.2 \\ \hline Cs\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cs & -2.92 \\ \hline Cu\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu & +0.521 \\ \hline Cu\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu\textsuperscript{+} & +0.153 \tiny{*(+0.16)} \\ \hline \end{tabular}$

2.3. Oxidant list between Cu²⁺ and Hg²⁺

$\textbf{TABLE 2.3}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline Cu\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu & +0.34 \\ \hline [Cu(CN)\textsubscript{2}]\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cu + 2CN\textsuperscript{-} & -0.43 \\ \hline F\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2F\textsuperscript{-} & +2.866 \\ \hline Fe\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe & -0.447 \\ \hline Fe\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe\textsuperscript{2+} & +0.771 \\ \hline Fe\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe & -0.04 \\ \hline [Fe(CN)\textsubscript{6}]\textsuperscript{3-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [Fe(CN)\textsubscript{6}]\textsuperscript{4-} & +0.36 \\ \hline Fe(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe + 2OH\textsuperscript{-} & -0.88 \\ \hline FeS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Fe + S\textsuperscript{2-} & -1.01 \\ \hline Ga\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ga & -0.549 \\ \hline Gd\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Gd & -2.279 \\ \hline \textcolor{red}{2H\textsuperscript{+} + 2e\textsuperscript{-}} & $\textcolor{red}{\xrightarrow{\text{\hspace{15 pt}}}}$ & \textcolor{red}{H\textsubscript{2} } & \textcolor{red}{0.00} \\ \hline H\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsuperscript{-} & -2.23 \\ \hline 2HBrO + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Br\textsubscript{2} + 2H\textsubscript{2}O & +1.60 \\ \hline HClO + H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsuperscript{-} + H\textsubscript{2}O & +1.482 \\ \hline 2HClO + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Cl\textsubscript{2} + 2H\textsubscript{2}O & +1.611 \\ \hline HClO\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HClO + H\textsubscript{2}O & +1.628 \\ \hline HO\textsubscript{2}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 3OH\textsuperscript{-} & +0.878 \\ \hline 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2} + 2OH\textsuperscript{-} & -0.8277 \\ \hline H\textsubscript{2}O\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsubscript{2}O & +1.776 \\ \hline H\textsubscript{4}XeO\textsubscript{6} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & XeO\textsubscript{3} + 3H\textsubscript{2}O & +3.0 \\ \hline Hf\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hf & -1.55 \\ \hline Hg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg & +0.851 \\ \hline 2Hg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg\textsubscript{2}\textsuperscript{2+} & +0.92 \\ \hline \end{tabular}$

2.4. Oxidant list between Hg₂²⁺ and MnO₄^–

$\textbf{TABLE 2.4}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline Hg\textsubscript{2}\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg & +0.7973 \\ \hline [HgBr\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + 4Br\textsuperscript{-} & +0.21 \\ \hline Hg\textsubscript{2}Cl\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg + 2Cl\textsuperscript{-} & +0.26808 \\ \hline [Hg(CN)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + 4CN\textsuperscript{-} & -0.37 \\ \hline [HgI\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + 4I\textsuperscript{-} & -0.04 \\ \hline HgS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Hg + S\textsuperscript{2-} & -0.70 \\ \hline Hg\textsubscript{2}SO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2Hg + SO\textsubscript{4}\textsuperscript{2-} & +0.62 \\ \hline I\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2I\textsuperscript{-} & +0.5355 \\ \hline I\textsubscript{3}\textsuperscript{-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 3I\textsuperscript{-} & +0.53 \\ \hline In\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In & -0.14 \\ \hline In\textsuperscript{2+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{+} & -0.40 \\ \hline In\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{2+} & -0.49 \\ \hline In\textsuperscript{3+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In\textsuperscript{+} & -0.44 \\ \hline In\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & In & -0.3382 \\ \hline K\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & K & -2.931 \\ \hline La\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & La & -2.52 \\ \hline Li\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Li & -3.04 \\ \hline Lu\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Lu & -2.28 \\ \hline Mg\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mg & -2.372 \\ \hline Mn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn & -1.185 \\ \hline MnO\textsubscript{2} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn\textsuperscript{2+} + 2H\textsubscript{2}O & +1.23 \\ \hline MnO\textsubscript{2} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn(OH)\textsubscript{2} + 2OH\textsuperscript{-} & -0.05 \\ \hline MnO\textsubscript{4}\textsuperscript{-} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{4}\textsuperscript{2-} & +0.56 \\ \hline MnO\textsubscript{4}\textsuperscript{-} + 8H\textsuperscript{+} + 5e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Mn\textsuperscript{2+} + 4H\textsubscript{2}O & +1.507 \\ \hline \end{tabular}$

2.5. Oxidant list between MnO₄^– and PbO₂

$\textbf{TABLE 2.5}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline MnO\textsubscript{4}\textsuperscript{-} + 2H\textsubscript{2}O + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{2} + 4OH\textsuperscript{-} & +0.558 \\ \hline MnO\textsubscript{4}\textsuperscript{2-} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & MnO\textsubscript{2} + 4OH\textsuperscript{-} & +0.60 \\ \hline Na\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Na & -2.71 \\ \hline Nd\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Nd & -2.323 \\ \hline Ni\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni & -0.257 \\ \hline [Ni(NH\textsubscript{3})\textsubscript{6}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni + 6NH\textsubscript{3} & -0.49 \\ \hline NiO\textsubscript{2} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni\textsuperscript{2+} + 2H\textsubscript{2}O & +1.593 \\ \hline NiO\textsubscript{2} + 2H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni(OH)\textsubscript{2} + 2OH\textsuperscript{-} & +0.49 \\ \hline NiOOH + H\textsubscript{2}O + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni(OH)\textsubscript{2} + OH\textsuperscript{-} & +0.49 \\ \hline NiS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ni + S\textsuperscript{2-} & +0.76 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 2H\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO\textsubscript{2} + H\textsubscript{2}O & -0.80 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 3H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HNO\textsubscript{2} + H\textsubscript{2}O & +0.92 \\ \hline NO\textsubscript{3}\textsuperscript{-} + 4H\textsuperscript{+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO + 2H\textsubscript{2}O & +0.957 \\ \hline NO\textsubscript{3}\textsuperscript{-} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & NO\textsubscript{2}\textsuperscript{-} + 2OH\textsuperscript{-} & +0.10 \\ \hline Np\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Np & -1.856 \\ \hline O\textsubscript{2} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}O\textsubscript{2} & +0.695 \\ \hline O\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2H\textsubscript{2}O & +1.229 \\ \hline O\textsubscript{2} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & HO\textsubscript{2}\textsuperscript{-} + OH\textsuperscript{-} & -0.08 \\ \hline O\textsubscript{2} + 2H\textsubscript{2}O + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 4OH\textsuperscript{-} & +0.401 \\ \hline O\textsubscript{3} + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & O\textsubscript{2} + H\textsubscript{2}O & +2.07 \\ \hline O\textsubscript{3} + H\textsubscript{2}O + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & O\textsubscript{2} + 2OH\textsuperscript{-} & +1.24 \\ \hline Pb\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb & -0.1262 \\ \hline Pb\textsuperscript{4+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb\textsuperscript{2+} & +1.67 \\ \hline PbO\textsubscript{2} + SO\textsubscript{4}\textsuperscript{2-} + 4H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & PbSO\textsubscript{4} + 2H\textsubscript{2}O & +1.69 \\ \hline \end{tabular}$

2.6. Oxidant list between PbS and Sn⁴⁺

$\textbf{TABLE 2.6}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline PbS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb + S\textsuperscript{2-} & -0.95 \\ \hline PbSO\textsubscript{4} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pb + SO\textsubscript{4}\textsuperscript{2-} & -0.3505 \\ \hline Pd\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pd & +0.987 \\ \hline [PdCl\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pd + 4Cl\textsuperscript{-} & +0.591 \\ \hline Pt\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt & +1.20 \\ \hline [PtBr\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt + 4Br\textsuperscript{-} & +0.58 \\ \hline [PtCl\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pt + 4Cl\textsuperscript{-} & +0.755 \\ \hline [PtCl\textsubscript{6}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & [PtCl\textsubscript{4}]\textsuperscript{2-} + 2Cl\textsuperscript{-} & +0.68 \\ \hline Pu\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pu & -2.03 \\ \hline Pu\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Pu\textsuperscript{3+} & +0.97 \\ \hline Ra\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ra & -2.92 \\ \hline Rb\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Rb & -2.93 \tiny{(** -2.98)} \\ \hline [RhCl\textsubscript{6}]\textsuperscript{3-} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Rh + 6Cl\textsuperscript{-} & +0.44 \\ \hline S + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & S\textsuperscript{2-} & -0.47627 \\ \hline S + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}S & +0.142 \\ \hline S\textsubscript{2}O\textsubscript{8}\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & 2SO\textsubscript{4}\textsuperscript{2-} & +2.05 \\ \hline Sc\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sc & -2.09 \\ \hline Se + 2H\textsuperscript{+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & H\textsubscript{2}Se & -0.399 \\ \hline [SiF\textsubscript{6}]\textsuperscript{2-} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 6F\textsuperscript{-} & -1.2 \\ \hline SiO\textsubscript{3}\textsuperscript{2-} + 3H\textsubscript{2}O + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 6OH\textsuperscript{-} & -1.697 \\ \hline SiO\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Si + 2H\textsubscript{2}O & -0.86 \\ \hline Sm\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sm & -2.304 \\ \hline Sn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn & -0.1375 \\ \hline Sn\textsuperscript{4+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn\textsuperscript{2+} & +0.151 \\ \hline \end{tabular}$

2.7. Oxidant list between [SnFe]^2- and Zr⁴⁺

$\textbf{TABLE 2.7}$
$\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}} \renewcommand{\arraystretch}{1.5} \begin{tabular}{| r c l | l |} \hline \cellcolor{lightgray} \text{\hspace{40pt}} \textcolor{white}{\textbf{Oxidants}} \text{\hspace{40pt}} &\cellcolor{lightgray} &\cellcolor{lightgray} \text{\hspace{30pt}} \textcolor{white}{\textbf{Reductants}} \text{\hspace{30pt}} &\cellcolor{lightgray} \textcolor{white}{\textbf{\textit{E}\textsuperscript{o}} \textbf{(Volt)}} \\ \hline [SnF\textsubscript{6}]\textsuperscript{2-} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn + 6F\textsuperscript{-} & -0.25 \\ \hline SnS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sn + S\textsuperscript{2-} & -0.94 \\ \hline Sr\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Sr & -2.89 \\ \hline TeO\textsubscript{2} + 4H\textsuperscript{+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Te + 2H\textsubscript{2}O & +0.593 \\ \hline Th\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Th & -1.90 \\ \hline Ti\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti & -1.630 \\ \hline Ti\textsuperscript{3+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti\textsuperscript{2+} & -0.37 \\ \hline Ti\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Ti\textsuperscript{3+} & 0.00 \\ \hline Tl\textsuperscript{+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Tl & -0.34 \\ \hline U\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & U & -1.79 \\ \hline U\textsuperscript{4+} + e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & U\textsuperscript{3+} & -0.61 \\ \hline V\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & V & -1.19 \\ \hline Y\textsuperscript{3+} + 3e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Y & -2.37 \\ \hline Zn\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn & -0.7618 \\ \hline [Zn(CN)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4CN\textsuperscript{-} & -1.26 \\ \hline [Zn(NH\textsubscript{3})\textsubscript{4}]\textsuperscript{2+} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4NH\textsubscript{3} & -1.04 \\ \hline Zn(OH)\textsubscript{2} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 2OH\textsuperscript{-} & -1.245 \\ \hline [Zn(OH)\textsubscript{4}]\textsuperscript{2-} + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + 4OH\textsuperscript{-} & -1.199 \\ \hline ZnS + 2e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zn + S\textsuperscript{2-} & -1.40 \\ \hline Zr\textsuperscript{4+} + 4e\textsuperscript{-} & $\xrightarrow{\text{\hspace{15 pt}}}$ & Zr & -1.539 \\ \hline \end{tabular}$

Electrochemical series & electrochemical cells explained

In the electrochemical series, in each half reaction, the left side contains the oxidant of the redox reaction, while the right side contains its reductant counterpart. The stronger the oxidant is, the weaker its reductant form is. In the list in which the potentials are arranged in descending order, the oxidizing strength of the reactants on the left side of the equations decreases from top to bottom, while the reducing power of reactants on the right side increases in the same direction.

A spontaneous reaction will occur if an oxidant of a half reaction reacts with a reductant of another half reaction that has a lower standard potential; combining these two half reactions results in an overall equation of the redox reaction.

An electrochemical cell is formed if the two half reactions (called half cells) of a redox reaction are not in direct contact, but electrons from the oxidization half cell (called anode) are allowed to flow to the reduction half cell (called cathode). An anode is where the oxidation reaction takes place and electrons are produced, and a cathode is where reduction reaction takes place, and electrons are consumed. Whether the electrode of an electrochemical cell is negative or positive is determined by its relative potential. During a discharge process, electrons flow from the anode to the cathode via an external load. Therefore, the anode has a lower potential, hence it is a negative electrode, while the cathode has a higher potential, hence it is a positive electrode. During the recharge process, although anode and cathode sites swap, the negative and positive electrodes do not change, as their potential is determined by the DC source used to supply energy to the electrochemical cell. An example of negative/positive electrodes can be found here.

A salt bridge is commonly used to supply negative ions (anions) to anodes and positive ions (cations) to cathodes to balance the charges consumed or generated in the half cells.

The standard potential of an electrochemical cell is obtained by subtracting the standard potential at the anode from the standard potential at the cathode.

E°_cell = E°_cathode – E°_anode

Note that the half-reaction that takes place at the anode is an oxidation reaction. To look up its E°_anode in the Electrochemical Series, which is compiled for reduction half-reaction by convention, we look for the reverse of that half-reaction. For example, if the oxidation half-reaction at the anode is Mg(s) → Mg²⁺(aq) + 2e^–, then the reverse of this reaction is the reduction half-reaction Mg²⁺(aq) + 2e^– → Mg(s), which has a standard potential of -2.372 V; therefore, its E°_anode is -2.372 V.

A redox reaction occurs spontaneously when an oxidant of a half reaction interacts with a reductant of another half reaction that has a lower standard potential. As a result, the standard potential E°_cell of a spontaneous redox reaction has a positive value. In fact, if the cell’s potential E_cell is greater than 0, then the redox reaction still takes place spontaneously even the reaction is not in the standard conditions.