A galvanic cell is based on the following half-reactions at...

A galvanic cell is based on the following half-reactions at $25^{\circ} \mathrm{C}$ : $$ \begin{aligned} \mathrm{Ag}^{+}+\mathrm{e}^{-} & \longrightarrow \mathrm{Ag} \\ \mathrm{H}_{2} \mathrm{O}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} & \longrightarrow 2 \mathrm{H}_{2} \mathrm{O} \end{aligned} $$ Predict whether $\mathscr{E}_{\text {cell }}$ is larger or smaller than $\mathscr{E}_{\text {cell }}^{\circ}$ for the following cases. a. $\left[\mathrm{Ag}^{+}\right]=1.0 M,\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=2.0 M,\left[\mathrm{H}^{+}\right]=2.0 M$ b. $\left[\mathrm{Ag}^{+}\right]=2.0 M,\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=1.0 M,\left[\mathrm{H}^{+}\right]=1.0 \times 10^{-7} M$

A galvanic cell is based on the following half-reactions at $25^{\circ} \mathrm{C}$ :
$$
\begin{aligned}
\mathrm{Ag}^{+}+\mathrm{e}^{-} & \longrightarrow \mathrm{Ag} \\
\mathrm{H}_{2} \mathrm{O}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} & \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}
\end{aligned}
$$
Predict whether $\mathscr{E}_{\text {cell }}$ is larger or smaller than $\mathscr{E}_{\text {cell }}^{\circ}$ for the following cases.
a. $\left[\mathrm{Ag}^{+}\right]=1.0 M,\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=2.0 M,\left[\mathrm{H}^{+}\right]=2.0 M$
b. $\left[\mathrm{Ag}^{+}\right]=2.0 M,\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=1.0 M,\left[\mathrm{H}^{+}\right]=1.0 \times 10^{-7} M$

Key Concepts

Galvanic Cell

A galvanic cell is an electrochemical cell that generates electrical energy from spontaneous redox reactions. It consists of two half-cells where oxidation and reduction occur separately and are connected by an external circuit and a salt bridge. The overall cell potential is determined by the potential differences between the two half-reactions under the cell conditions.

Standard Cell Potential

The standard cell potential is the voltage measured when all reactants and products are in their standard states, typically 1 M for solutions, 1 atm for gases, and pure solids or liquids as applicable. It serves as a benchmark for comparing cell performance under non?standard or varying concentration conditions.

Nernst Equation

The Nernst equation relates the electrode potential to the concentrations (or pressures) of the reacting species. By incorporating the reaction quotient, it allows for the calculation of the cell potential under non-standard conditions. This equation shows how deviations from standard concentrations affect the overall potential of the cell.

Reaction Quotient (Q)

The reaction quotient, symbolized as Q, is a dimensionless number that reflects the current concentrations of reactants and products in a reaction. In the context of electrochemistry, Q is used in the Nernst equation to determine how far the cell is from equilibrium, influencing the cell potential accordingly.

Concentration Effects on Cell Potential

The cell potential is influenced by the concentrations of the chemical species involved. Increasing the concentration of reactants or decreasing the concentration of products in a reduction or oxidation half-cell can shift the electrode potential. This effect determines whether the measured cell potential will be higher or lower than the standard cell potential under given conditions.

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