## Standard Electrode Potential

 1.2 Standard Electrode Potential

 Definition of Electrode Potential Potential difference produced when an equilibrium is established between metal M and the aqueous solution containing metal $$M^{n+}$$ions in a half-cell.

 The Electrode Potential of A Cell Electrode potential cannot be measured directly. The value is determined based on the difference of electrode potential between two half-cells. The electrode potential can be measured by pairing up the electrode to the standard reference electrode system. The international consensus is the standard hydrogen electrode.

 Standard Hydrogen Electrode Function of platinum(IV) oxide, $$PtO_2$$: To increase the surface area of platinum, Pt to adsorb hydrogen gas, $$H_2$$. This is done so that hydrogen molecules are in closer contact with hydrogen ions, $$H^+$$ in the solution. Half equation of the hydrogen half-cell; $$2H^+ (aq) +2e^- \rightleftharpoons H_2(g)$$ The standard hydrogen electrode potential, Eº is given the value of 0.00 V: $$H^+ (aq) +e^- \rightleftharpoons \frac{1}{2}H_2(g) \hspace{1cm}E^0=0.00V$$

 Standard Electrode Potential Value, Eº Apparatus set-up to determine standard electrode potential, Eº of zinc is as below: Since the standard hydrogen potential is 0.00 V, the voltmeter reading of 0.76 V shows the electrode potential of zinc. Zinc, Zn has a greater tendency to release electrons compared to hydrogen. Hence, zinc, Zn becomes the negative terminal. Electrons move from zinc electrode, Zn (negative terminal) to platinum electrode, Pt (positive terminal) through the connecting wires.

 Electrode Zinc Hydrogen Terminal Negative Positive Half equation $$Zn(p) \rightarrow Zn^{2+} (aq) +2e^-$$ $$2H^{+} (aq) +2e^-\rightarrow H_2(g)$$ Reaction Oxidation Reduction Standard electrode potential for half cell $$Zn^{2+} (aq) +2e^- \rightleftharpoons Zn(s)\\ \,\\ E^0=-0.76V$$ The negative symbol shows that zinc electrode is the negative terminal when connected to the standard hydrogen electrode

Oxidising Agents and Reducing Agents Based on The Value of Standard Electrode Potential
• The standard electrode potential, Eº is also known as the standard reduction potential.
• All half-cell equations are written as reduction.
• Eº value is a measure of the tendency of a substance to accept or donate electrons.
• $$\text{Oxidising agent }+ \text{electron} \rightleftharpoons \text{Reducing agent}$$
 Standard Electrode Potential Series

 Comparison of standard electrode potential, Eº value
• Is used to determine whether silver, Ag or magnesium, Mg is an oxidising agent or reducing agent.
 When Eº Value of Ag is More Positive When Eº Value of Ag is More Negative Silver ion, 𝐴𝑔+ on the left side is a stronger oxidising agent. Magnesium atom, Mg on the right side is a stronger reducing agent. It is easier for 𝐴𝑔+ ion to receive electrons and undergo reduction. It is easier for magnesium atom, Mg to release electrons and undergo oxidation. Conversely, silver atom, Ag on the right side is difficult to release electrons. Conversely, magnesium ion, 𝑀𝑔2+Mg2+ on the left side is difficult to accept electrons.

 The Relationship between Eº value to The Strength of a Substance as an Oxidizing Agent and a Reducing Agent

 Molecules or Ions with a More Positive or Less Negative Standard Electrode Potential Value Eº Atoms or Ions with a More Negative or Less Positive Standard Electrode Potential Value Eº Has a greater tendency to accept electrons. Has a greater tendency to release electrons. Easier to undergo reduction reaction. Easier to undergo oxidation reaction. A stronger oxidising agent. A stronger reducing agent.

## Standard Electrode Potential

 1.2 Standard Electrode Potential

 Definition of Electrode Potential Potential difference produced when an equilibrium is established between metal M and the aqueous solution containing metal $$M^{n+}$$ions in a half-cell.

 The Electrode Potential of A Cell Electrode potential cannot be measured directly. The value is determined based on the difference of electrode potential between two half-cells. The electrode potential can be measured by pairing up the electrode to the standard reference electrode system. The international consensus is the standard hydrogen electrode.

 Standard Hydrogen Electrode Function of platinum(IV) oxide, $$PtO_2$$: To increase the surface area of platinum, Pt to adsorb hydrogen gas, $$H_2$$. This is done so that hydrogen molecules are in closer contact with hydrogen ions, $$H^+$$ in the solution. Half equation of the hydrogen half-cell; $$2H^+ (aq) +2e^- \rightleftharpoons H_2(g)$$ The standard hydrogen electrode potential, Eº is given the value of 0.00 V: $$H^+ (aq) +e^- \rightleftharpoons \frac{1}{2}H_2(g) \hspace{1cm}E^0=0.00V$$

 Standard Electrode Potential Value, Eº Apparatus set-up to determine standard electrode potential, Eº of zinc is as below: Since the standard hydrogen potential is 0.00 V, the voltmeter reading of 0.76 V shows the electrode potential of zinc. Zinc, Zn has a greater tendency to release electrons compared to hydrogen. Hence, zinc, Zn becomes the negative terminal. Electrons move from zinc electrode, Zn (negative terminal) to platinum electrode, Pt (positive terminal) through the connecting wires.

 Electrode Zinc Hydrogen Terminal Negative Positive Half equation $$Zn(p) \rightarrow Zn^{2+} (aq) +2e^-$$ $$2H^{+} (aq) +2e^-\rightarrow H_2(g)$$ Reaction Oxidation Reduction Standard electrode potential for half cell $$Zn^{2+} (aq) +2e^- \rightleftharpoons Zn(s)\\ \,\\ E^0=-0.76V$$ The negative symbol shows that zinc electrode is the negative terminal when connected to the standard hydrogen electrode

Oxidising Agents and Reducing Agents Based on The Value of Standard Electrode Potential
• The standard electrode potential, Eº is also known as the standard reduction potential.
• All half-cell equations are written as reduction.
• Eº value is a measure of the tendency of a substance to accept or donate electrons.
• $$\text{Oxidising agent }+ \text{electron} \rightleftharpoons \text{Reducing agent}$$
 Standard Electrode Potential Series

 Comparison of standard electrode potential, Eº value
• Is used to determine whether silver, Ag or magnesium, Mg is an oxidising agent or reducing agent.
 When Eº Value of Ag is More Positive When Eº Value of Ag is More Negative Silver ion, 𝐴𝑔+ on the left side is a stronger oxidising agent. Magnesium atom, Mg on the right side is a stronger reducing agent. It is easier for 𝐴𝑔+ ion to receive electrons and undergo reduction. It is easier for magnesium atom, Mg to release electrons and undergo oxidation. Conversely, silver atom, Ag on the right side is difficult to release electrons. Conversely, magnesium ion, 𝑀𝑔2+Mg2+ on the left side is difficult to accept electrons.

 The Relationship between Eº value to The Strength of a Substance as an Oxidizing Agent and a Reducing Agent

 Molecules or Ions with a More Positive or Less Negative Standard Electrode Potential Value Eº Atoms or Ions with a More Negative or Less Positive Standard Electrode Potential Value Eº Has a greater tendency to accept electrons. Has a greater tendency to release electrons. Easier to undergo reduction reaction. Easier to undergo oxidation reaction. A stronger oxidising agent. A stronger reducing agent.