The following sketch is of a voltaic cell consisting of two...

The following sketch is of a voltaic cell consisting of two standard electrodes for two metals, M and N: Use the standard reduction potentials of these halfreactions to answer the questions that follow: $$\begin{array}{c} \mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \mathrm{Ag}(\mathrm{s}) \\ \mathrm{Zn}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}(\mathrm{s}) \end{array}$$ $$\begin{array}{l} \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{s}) \\ \mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}(\mathrm{s}) \end{array}$$ (a) Determine which pair of these half-cell reactions leads to a cell reaction with the largest positive cell potential, and calculate its value. Which couple is at the anode and which at the cathode? (b) Determine which pair of these half-cell reactions leads to the cell with the smallest positive cell potential, and calculate its value. Which couple is at the anode and which is at the cathode?

The following sketch is of a voltaic cell consisting of two standard electrodes for two metals, M and N:
Use the standard reduction potentials of these halfreactions to answer the questions that follow:
$$\begin{array}{c}
\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \mathrm{Ag}(\mathrm{s}) \\
\mathrm{Zn}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}(\mathrm{s})
\end{array}$$
$$\begin{array}{l}
\mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{s}) \\
\mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}(\mathrm{s})
\end{array}$$
(a) Determine which pair of these half-cell reactions leads to a cell reaction with the largest positive cell potential, and calculate its value. Which couple is at the anode and which at the cathode?
(b) Determine which pair of these half-cell reactions leads to the cell with the smallest positive cell potential, and calculate its value. Which couple is at the anode and which is at the cathode?

Key Concepts

Electrode Roles (Anode and Cathode)

In an electrochemical cell, the anode is where oxidation occurs (loss of electrons), and the cathode is where reduction occurs (gain of electrons). Correctly assigning these roles based on the standard reduction potentials is crucial for determining the direction of electron flow and for calculating the cell's overall potential. The half-cell with the lower reduction potential typically serves as the anode, while the half-cell with the higher reduction potential acts as the cathode.

Voltaic Cell

A voltaic cell is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. It consists of two half-cells, each containing an electrode and an electrolyte, where oxidation occurs in one half-cell (anode) and reduction takes place in the other (cathode). The electrical energy is generated by the difference in chemical potential between the two electrodes.

Half-Cell Reactions

Half-cell reactions represent the individual oxidation and reduction processes occurring in each half of an electrochemical cell. These reactions involve the transfer of electrons, with one reaction losing electrons (oxidation) and the other gaining electrons (reduction). They are crucial for understanding how electrons flow from one electrode to another, driving the cell's overall reaction.

Standard Reduction Potentials

Standard reduction potentials are values assigned to half-cell reactions under standard conditions. They indicate the tendency of a chemical species to be reduced (gain electrons). A more positive standard reduction potential means a greater likelihood of reduction, whereas a less positive or negative value indicates a tendency to be oxidized. These potentials are essential for predicting the direction of electron flow in an electrochemical cell.

Cell Potential Calculation

The cell potential of a voltaic cell is calculated by taking the difference between the cathode's standard reduction potential and the anode's standard reduction potential. This calculation indicates the overall driving force behind the redox reaction. A positive value confirms that the reaction is spontaneous under standard conditions, with a larger positive value representing a greater driving force.

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