Question

A student needs to calculate the standard potential of a electrochemical cell formed by a zinc electrode and a silver electrode. The concentration of Zn2+ ions in the zinc half-cell is 1.0 M and the concentration of Ag+ ions in the silver half-cell is 0.1 M. The measured potential of the cell is 1.95 V. What is the standard potential of the cell?

Answer 1

To calculate the standard potential of the electrochemical cell, we need to use the Nernst equation:E_cell = E_cell -  RT/nF  * ln Q where E_cell is the measured potential of the cell, E_cell is the standard potential of the cell, R is the gas constant  8.314 J/molK , T is the temperature in Kelvin  assuming 298 K, which is 25C , n is the number of electrons transferred in the redox reaction, F is the Faraday constant  96,485 C/mol , and Q is the reaction quotient.For the given cell, the redox reaction is:Zn s  + 2Ag+ aq  -> Zn2+ aq  + 2Ag s The number of electrons transferred, n, is 2.The reaction quotient, Q, is given by:Q = [Zn2+]/[Ag+]^2Plugging in the given concentrations:Q =  1.0 M / 0.1 M ^2 = 100Now, we can rearrange the Nernst equation to solve for E_cell:E_cell = E_cell +  RT/nF  * ln Q Plugging in the given values and constants:E_cell = 1.95 V +   8.314 J/molK  *  298 K  /  2 * 96,485 C/mol   * ln 100 E_cell = 1.95 V +  0.0129 V  * ln 100 E_cell = 1.95 V +  0.0129 V  * 4.605E_cell  1.95 V + 0.0594 VE_cell  2.0094 VTherefore, the standard potential of the electrochemical cell is approximately 2.0094 V.