 # Concentration affecting the voltage of a voltaic cell

Relate cell potentials to Gibbs energy changes Use the Nernst equation to determine cell potentials at nonstandard conditions Perform calculations that involve converting between cell potentials, free energy changes, and equilibrium constants The Nernst Equation enables the determination of cell potential under non-standard conditions.

It relates the measured cell potential to the reaction quotient and allows the accurate determination of equilibrium constants including solubility constants. The Effect of Concentration on Cell Potential: The Nernst equation is arguably the most important relationship in electrochemistry. We can therefore determine the spontaneous direction of any redox reaction under any conditions, as long as we have tabulated values for the relevant standard electrode potentials.

Determine the number of electrons transferred during the redox process. Then use the Nernst equation to find the cell potential under the nonstandard conditions. The overall reaction involves the net transfer of two electrons: Recall that the overall reaction for this cell is as follows: Suppose that the cell initially contains 1.

Thus the value of Q will increase further, leading to a further decrease in Ecell. When the concentrations in the two compartments are the opposite of the initial concentrations i. As the reaction progresses, log Q increases, and Ecell decreases. At this point, the system will have reached equilibrium. If neither of the electrodes dissolves completely, thereby breaking the electrical circuit, the cell voltage will eventually reach zero.

Concentration Cells A voltage can also be generated by constructing an electrochemical cell in which each compartment contains the same redox active solution but at different concentrations. The voltage is produced as the concentrations equilibrate.

### Step 4: Cells in non-standard conditions

Suppose, for example, we have a cell with 0. The cell diagram and corresponding half-reactions are as follows: Write the overall reaction that occurs in the cell.

Determine the number of electrons transferred. Substitute this value into the Nernst equation to calculate the voltage. A This is a concentration cell, in which the electrode compartments contain the same redox active substance but at different concentrations. The overall reaction is as follows: One beaker contains 1.

## How does concentration affect galvanic cell?

If the relevant electrochemical reaction in both compartments is the four-electron reduction of oxygen to water: Equilibrium constants of this magnitude are virtually impossible to measure accurately by direct methods, so we must use alternative methods that are more sensitive, such as electrochemical methods. In one compartment, the cell contains a silver wire inserted into a 1. The overall cell reaction is as follows: One compartment contains a silver wire inserted into a 1. You then insert a Pb electrode into each compartment and close the circuit. Your voltmeter shows a voltage of 230 mV. What is Ksp for PbSO4? Report your answer to two significant figures. From the information given, write the equation for Ksp. Determine the number of electrons transferred in the electrochemical reaction. A You have constructed a concentration cell, with one compartment containing a 1. As for any concentration cell, the voltage between the two compartments can be calculated using the Nernst equation. 