Q21.127 CP - Chemistry: Molecular Nature Of Matter And Change

Question

In Appendix D, standard electrode potentials range from about $\text{ + 3}$to $\text{- 3 V}$. Thus, it might seem possible to use a half-cell from each end of this range to construct a cell with a voltage of approximately $\text{6 V}$ . However, most commercial aqueous voltaic cells have ${\text{E}}^{\text{o}}$ values of $\text{1.5}$ to $\text{2 V}$ . Why are there no aqueous cells with significantly higher potentials?

Step-by-Step Solution

Answer

If the cell potential were higher, electrolysis of water will occur and form hydrogen and oxygen gases.

Step 1: Concept Introduction

The standard electrode potential is a measurement of the equilibrium potential. The potential of the electrode is the difference in potential between the electrode and the electrolyte. The electrode potential is known as the standard electrode potential when the concentrations of all the species involved in a semi-cell are equal. A galvanic cell or voltaic cell is an electrochemical cell that converts the chemical energy of spontaneous redox reactions into electrical energy.

Step 2: Aqueous Cells

Aqueous cells have $\text{1.5 V}$to $\text{2 V}$potentials because higher half-cell potentials react with water, instead of interacting with the other electrode. If the cell potential were higher, electrolysis of water will occur and form hydrogen and oxygen gases.

 

Therefore, ${\text{H}}_{\text{2}}$and ${\text{O}}_{\text{2}}$ gases form during electrolysis if the cell potential is higher.