Question

Choose the best reducing agent from the list below.

A. Ni²⁺(aq)

B. Ag(s)

C.F₂(g)

D. Fe(s)

I expected the answer to be A because the strongest reducing agent would be the most likely to be oxidized. Wouldn't a cation want to give up it's electrons, or be oxidized more than a metal solid or a highly electronegative halogen? The correct answer is D. Will someone please explain why this is?

Answer 1

Given potentials are reduction potentials.

An oxidising agent is having higher reduction potential & A reducing agent is having lower reduction potential.

Remember that

An oxidising agent will oxidise any reducing agent.A reducing agent will reduce any oxidising agent.

Also lower reduction potential metal displaces higher reduction potential value metal.

So for the best reducing agent will have lower reducing agent.

Ni²⁺(aq) + 2 e^– Ni(s) : E^o = -0.25 V

Ag(s) Ag⁺(aq) + e^–   : E^o = -0.7994V

F₂(g) +2e^- 2F^-(aq) : E^o = +2.87 V

Fe(s) Fe²⁺(aq) + 2 e^– : E^o = +0.44V

Since the reduction potential of Ni²⁺ is less so Ni²⁺ is the best reducing agent.