Among the 3d transition series, copper is the only metal that does not liberate hydrogen gas from dilute mineral acids. This is because it has a positive standard reduction potential ( E^ _ Cu ²⁺/ Cu = +0.34 V ). Which of the following thermodynamic factors is responsible for this positive value?

Step-by-step solution

The standard reduction potential ( E^ ) of a metal depends on three thermodynamic factors: enthalpy of atomization ( _ a H^ ), ionization enthalpy ( _ i H^ ), and hydration enthalpy ( _ hyd H^ ). For copper, the sum of its high enthalpy of atomization and high ionization enthalpies is very large. This high energy required to transform Cu _ (s) to Cu ²⁺_ (aq) is not balanced by its negative hydration enthalpy. As a result, the overall standard reduction potential for the Cu ²⁺/ Cu couple is positive ( +0.34 V ), mak