Mention the important applications of standard hydrogen electrode. The standard electrode potential for Fe^+3/Fe^+2 and I2/I^ are +0.77V and +0.54V respectively. i) Draw the standard cell notation.…

Applications of Standard Hydrogen Electrode (SHE)

The Standard Hydrogen Electrode (SHE) serves as a reference electrode in electrochemical cells due to its assigned standard electrode potential of 0 V. Its key applications include:

1. Reference Electrode: Used as a standard to measure the electrode potentials of other half-cells.
2. pH Measurement: Helps in calibrating pH meters and determining hydrogen ion concentrations.
3. Electrochemical Series: Provides a baseline for constructing the electrochemical series of metals and non-metals.
4. Corrosion Studies: Assists in studying corrosion tendencies of metals by comparing their potentials against SHE.
5. Battery Development: Used in designing and optimizing electrochemical cells, including fuel cells and rechargeable batteries.

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Solution to the Given Problem

i) Standard Cell Notation

The standard cell is constructed using the given half-cells:

• $\mathrm{Fe}{}^{3+}/\mathrm{Fe}{}^{2+}$ with $E^{\circ }=+0.77\text{V}$
• $\mathrm{I}{}_2/\mathrm{I}{}^{-}$ with $E^{\circ }=+0.54\text{V}$

Since $\mathrm{Fe}{}^{3+}/\mathrm{Fe}{}^{2+}$ has a higher (more positive) reduction potential, it acts as the cathode, and $\mathrm{I}{}_2/\mathrm{I}{}^{-}$ acts as the anode.

The standard cell notation is:

Pt(s) | I⁻(1 M) | I₂(s) || Fe²⁺(1 M), Fe³⁺(1 M) | Pt(s)

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ii) Identification of Anode and Cathode

• Anode (Oxidation): $\mathrm{I}{}^{-}$ is oxidized to $\mathrm{I}{}_2$ (lower reduction potential).
• Cathode (Reduction): $\mathrm{Fe}{}^{3+}$ is reduced to $\mathrm{Fe}{}^{2+}$ (higher reduction potential).

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iii) Cell Reaction

The overall cell reaction is obtained by combining the half-reactions:

1. Anode (Oxidation): $$2I^{-}\to I_2+2e^{-}$$
2. Cathode (Reduction): $$2F{e}^{3+}+2e^{-}\to 2F{e}^{2+}$$ Net Cell Reaction: $$2F{e}^{3+}+2I^{-}\to 2F{e}^{2+}+I_2$$

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iv) Calculation of Standard Cell Potential

The standard cell potential ($E_{\text{cell}}^{\circ }$) is calculated using the formula: $$E_{\text{cell}}^{\circ }=E_{\text{cathode}}^{\circ }-E_{\text{anode}}^{\circ }$$ Substituting the given values: $$E_{\text{cell}}^{\circ }=(+0.77\text{V})-(+0.54\text{V})=+0.23\text{V}$$ Standard cell potential = 0.23 V (positive, so the reaction is spontaneous).