Cell Potential: Standard Electrode Potentials and Nernst Quiz

According to IUPAC standards, electrode potentials are reported as standard reduction potentials. This allows for a uniform comparison across different half-cells by treating every electrode as a cathode in a hypothetical cell.

The Standard Hydrogen Electrode (SHE) is the universal reference point. All other electrode potentials are determined by measuring the potential difference between the given half-cell and the SHE under standard conditions.

This is true. A positive cell potential corresponds to a negative change in Gibbs Free Energy (delta G = -nFE), which is the thermodynamic criteria for a spontaneous process.

In electrochemistry, 'n' refers to the stoichiometric number of electrons exchanged in the balanced redox reaction. This is a dimensionless quantity derived from the half-reactions.

Increasing reactant concentration (or decreasing product concentration) decreases the reaction quotient (Q). Since the Nernst Equation subtracts a term involving log(Q), a smaller Q results in a higher cell potential.

Standard conditions are defined as a temperature of 298.15 K (25 degrees C), an effective concentration (activity) of 1.0 M for solutes, and a partial pressure of 1.0 atm for gases.

This is true. At equilibrium, the cell potential (E) is zero. By setting E to zero in the Nernst Equation, the standard potential (E0) can be directly related to the log of the equilibrium constant.

R is the universal gas constant, valued at 8.314 Joules per mole-Kelvin. In the Nernst Equation, it links thermal energy to electrical work.

The Nernst Equation involves T (Temperature), R (Gas Constant), F (Faraday Constant), n (electrons), and Q (Reaction Quotient). Volume is not explicitly a variable, though it affects concentration.

A high positive E0 indicates a strong tendency to gain electrons (be reduced). Therefore, the species is an excellent oxidizing agent because it readily pulls electrons from other substances.

This is true. Unlike Gibbs Free Energy, which is extensive and scales with the amount of substance, the potential (Voltage) is a measure of energy per charge and remains constant regardless of the reaction scale.

At standard temperature, the constant term (2.303RT/F) simplifies to approximately 0.0592 Volts. This is frequently used in calculations to quickly find the effect of concentration changes on potential.

In the reaction quotient, the activity of pure solids like Cu(s) is defined as 1. Therefore, Q is 1 divided by the concentration of the aqueous Copper ions.

Temperature, concentration, and pressure are the variables in the Nernst Equation that deviate from standard state. A salt bridge is necessary for the cell to function but does not inherently change the E0 to E transition.

This is false. The Nernst Equation describes the fundamental relationship between chemical activity and electrical potential for any electrochemical system, whether it is producing power or being driven by an external source.