Question

(a) What is a standard reduction potential? (b) What is the standard reduction potential of a standard hydrogen electrode?

Short answer

(a) A standard reduction potential is the tendency of a chemical species to reduce or accept electrons under standard conditions (298 K, 1 atm pressure, and 1 M concentration for ions). It is measured in volts (V), and more positive values indicate greater tendencies for species to be reduced, while more negative values indicate less tendency to be reduced. (b) The standard reduction potential of a standard hydrogen electrode (SHE), used as a reference electrode to compare the reduction potentials of other species, is assigned a value of 0 volts (V) under standard conditions.

Step-by-step solution

(a) Defining Standard Reduction Potential

A standard reduction potential is the tendency of a chemical species to reduce or accept electrons under standard conditions, which include a temperature of 298 K, a pressure of 1 atmosphere, and a concentration of 1 M for the ions involved in the reaction. It is measured in volts (V) and provides a quantitative means of assessing the relative reactivity of various half-reactions in electrochemical cells. More positive standard reduction potential values indicate greater tendencies for species to be reduced, while more negative values indicate less tendency to be reduced.

(b) Standard Reduction Potential of a Standard Hydrogen Electrode

The standard hydrogen electrode (SHE) is a standard reference electrode which is used to compare the reduction potentials of other species. It consists of a platinum electrode immersed in a solution containing hydrogen ions (H^+) at a concentration of 1 M, and it is in contact with hydrogen gas at a pressure of 1 atmosphere. By definition, the standard reduction potential of the standard hydrogen electrode is assigned a value of 0 volts (V). This value serves as a reference point for comparing the standard reduction potentials of other half-reactions, and all other standard reduction potentials are measured relative to this value.