Question

How can one construct a galvanic cell from two substances, each having a negative standard reduction potential?

Short answer

To construct a galvanic cell using two substances A and B with negative standard reduction potentials, first determine the anode (Substance A) and cathode (Substance B) based on their reduction potentials. Then, set up the cell with the notation: Substance A | A^n+ || B^n+ | Substance B. Fill two containers with electrolyte solutions of A and B, place electrodes made of each substance in their respective containers, and connect them with a conducting wire including a voltmeter. Finally, connect the containers using a salt bridge to maintain charge balance.

Step-by-step solution

Identify the substances and their standard reduction potentials

For the sake of this example, let's assume we are given two substances, A and B, with their standard reduction potentials: Substance A has a standard reduction potential Eº_A of -1.2 V, and Substance B has a standard reduction potential Eº_B of -0.8 V.

Determine the anode and cathode

To form a spontaneous redox reaction, the substance with the higher reduction potential should be the cathode, and the substance with a lower reduction potential should be the anode. In this case, Eº_B (-0.8 V) is higher than Eº_A (-1.2 V). Therefore, Substance B will act as the cathode, and Substance A will be the anode for this galvanic cell.

Describe the cell notation

Now that we've identified the anode and cathode, we can write the complete cell notation. The cell notation for this galvanic cell is given by: Anode | Anode electrolyte || Cathode electrolyte | Cathode For our example: Substance A | A^n+ || B^n+ | Substance B

Set up the galvanic cell

To set up the galvanic cell, follow these steps: 1. Place two containers (beakers) side-by-side, one for each half-cell. 2. Fill each container with an electrolyte solution that contains the ions of Substance A and Substance B, respectively. 3. Place an electrode made of Substance A in the container with its electrolyte and an electrode made of Substance B in the container with its electrolyte. 4. Connect the two electrodes with a conducting wire, including a voltmeter in the circuit to measure the cell potential. 5. Connect the two containers via a salt bridge (a U-shaped tube filled with an inert electrolyte). This allows the flow of ions between the half-cells and helps in maintaining charge neutrality of the solutions. Now you have successfully constructed the galvanic cell using two substances with negative standard reduction potentials.