What value is associated with the half-reaction Ag+(aq) + e− → Ag(s)?

The value associated with the half-reaction Ag+(aq) + e− → Ag(s) is indeed +0.80 V. This value represents the standard reduction potential for the silver ion being reduced to solid silver. The standard reduction potential is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced.

In this context, a positive value indicates that the half-reaction is favorable and occurs spontaneously in the direction written. The standard reduction potential for silver ions is often referenced in electrochemical cells, where it outlines their ability to gain electrons under standard conditions (1 M concentration, 25 degrees Celsius, and 1 atm pressure for gases).

Lower potential values, whether positive or negative, would correspond to half-reactions that are less favorable as reduction processes compared to the standard hydrogen electrode, which is assigned a potential of 0 V. Therefore, the +0.80 V for Ag+ indicates a strong tendency for the ion to be reduced, making it a good oxidizing agent in electrochemical applications.