-1

How can we predict the order of reduction potentials for given elements? Consider the reactivity of metals, there is a standard explanation to determine reactivity. Eg. Sodium is more reactive than lithium due its larger ionic radius. Hence we have intuition for the order of reactivity. However, for reduction potentials, I can't seem to find an explanation. Unintuitively, the reduction potential of sodium is actually lower than that of lithium, meaning that reduction potential cannot be determined by reactivity, so there must be something else going on.

The best explanation so far, states that reduction potential is determined by ionisation energy and hydration energy, a mixture of the two? Could this be correct?

Comprehensive explanation of how we can build intuition for reduction potential would be great. Could you provide links or materials to learn about this?

Edit: Answers always explain that the reduction potential is measured relative to the hydrogen potential which makes sense. However, what are the underlying principles? Eg. For reactivity with metals, we could obviously just react them together and determine a reactivity series. However, we have an explanation for this reactivity series, which is what I want for reduction potential. Could reduction potential be determined by ionisation energy and hydration energy?

Stark
  • 89
  • 5
  • 1
    Do thorough searching, similar questions were asked multiple times on this site. Be aware of kinetic reactivity and thermodynamic reactivity are 2 different things. In Li and Na case, their order is mutually switched. Na reacts faster, but Li releases more energy per molar amount (free molar enthalpy). – Poutnik Mar 30 '24 at 10:03
  • "Sodium is more reactive than lithium due its larger ionic radius." That sounds like a proximate rather than ultimate explanation. What definition do you use for reactivity? Oxidation potential is a factor in the definition provided at the Wikipedia: "lose electrons (oxidize) more readily to form positive ions;" – Buck Thorn Mar 30 '24 at 19:28
  • related: https://chemistry.stackexchange.com/questions/87514/why-are-not-all-metals-included-in-the-reactivity-series/87529#87529 – Buck Thorn Mar 31 '24 at 10:10

1 Answers1

0

I think you are asking about the measurement of Standard Reduction potential. It is done by building a electrochemical cell, where the element under observation is taken as an electrode and the other half cell is the SHE (Standard Hydrogen Electrode). SHE acts as a reference point(its reduction potential is assigned as 0 V) and based on the unknown electrode it will get oxidised or reduced. In this manner we can find Std Reduction potential values.

Lakshya Dubey
  • 1
  • 1