AAMC 7 #48 Electron Affinity

[KO5590]

The following reaction occurs spontaneously.

Cd(s) + 2 H+(aq) --> Cd2+(aq) + H2(g)

Which of the following has the highest electron affinity?

a.) Cd(s)
b.) H+ (aq)
c.) Cd2+(aq)
d.) H2(g)

ANSWER: B. Reaction equation shows the reduction of H+ by Cd. Because the H+ accepts the electron readily from Cd, it can be determined that H+ has the highest electron affinity.

My confusion: Wouldn't H+ have a negative electron affinity because H+ is filling it's valency and thus favorable? I think I may be confused on + vs - electron affinities; Could someone please help explain?!? Thanks for your time!

---

Members don't see this ad.

 

[mcgst9]

The following reaction occurs spontaneously.

Cd(s) + 2 H+(aq) --> Cd2+(aq) + H2(g)

Which of the following has the highest electron affinity?

a.) Cd(s)
b.) H+ (aq)
c.) Cd2+(aq)
d.) H2(g)

ANSWER: B. Reaction equation shows the reduction of H+ by Cd. Because the H+ accepts the electron readily from Cd, it can be determined that H+ has the highest electron affinity.

My confusion: Wouldn't H+ have a negative electron affinity because H+ is filling it's valency and thus favorable? I think I may be confused on + vs - electron affinities; Could someone please help explain?!? Thanks for your time!

Not really sure what you are talking about with negative affinities.

I think you are thinking too in-depth with this question. It is asking specifically to the equation given. H+ has the highest electron affinity in that equation, because it is the species that is reduced. Cd readily gives up it's electrons to H+, and thus it is the most easily oxidized.

To make it even simpler, you ignore the products because they are irrelevant to the topic at hand as the reaction does not go in reverse (or at least, not to a large degree). Basically, you are looking at the reactants and deciding which one takes electrons easier.

 

[navho77]

Also, the key word here is "spontaneous". When you see a redox reaction and discussion of spontaneity, you should think about using comparative reduction potentials to make your choice. While your reasoning may be plausible in a loose way, it's just not the concept being tested by the question.