Relative Strengths of Oxidizing and Reducing Agents

non-metals: gain electrons and are good oxidizing agents.

metals: lose electrons and are good reducing agents.

Brief Activity Series

Strong Reducing Agent.

Strong Oxidizing Agent

Li+(aq) + e- ↔ Li(s) Eo = -3.04 V (non-spontaneous as written)

Li+(aq) + e- → Li(s) Eo = -3.04 V (non-spontaneous)

Li+ is acting as a oxidizing agent (gaining an electron), but the negative sign shows this to be a non-spontaneous reaction.

Li(s) → Li+(aq) + e- Eo = +3.04 V (spontaneous)

Li(s) is acting as a reducing agent (losing an electron) and the positive sign shows this to be a spontaneous reaction.

So Li(s) makes a much better reducing agent than Li+(aq) makes as an

oxidizing agent.

Li+(aq) + e- ↔ Li(s) Eo = -3.04 V (non-spontaneous as written)

Li+(aq) + e- → Li(s) Eo = -3.04 V (non-spontaneous)

Li+ is acting as a oxidizing agent (gaining an electron), but the negative sign shows this to be a non-spontaneous reaction.

Li(s) → Li+(aq) + e- Eo = +3.04 V (spontaneous)

Li(s) is acting as a reducing agent (losing an electron) and the positive sign shows this to be a spontaneous reaction.

Zn2+(aq) + 2e- ↔ Zn(s) Eo = -0.76 V (non-spontaneous as written

Zn2+(aq) + 2e- → Zn(s) Eo = -0.76 V Zn2+ is acting as an oxidizing agent. Is it a stronger or weaker oxidizing agent than Li+? stronger,less

negative

Zn(s) → Zn2+(aq) + 2e- Eo = +0.76 V Zn(s) is acting as a reducing agent. Is it a stronger or weaker reducing agent than Li(s)?

Weaker, +3.04 > +0.76

Li(s) can reduce Zn2+(aq) or Zn2+(aq) can oxidize Li(s)

2Li(s) + Zn2+(aq) → 2Li+(aq) + Zn(s) Eocell= +3.04 + -0.76 = +2.28 V

What can be said about Mg(s) and Al3+(aq)?

What about Al3+(aq) and Zn2+(aq)?

Mg(s) can reduce Al3+(aq) or Al3+(aq) can oxidize Mg(s).

Nothing will happen, they are both fully oxidized.

Cr(s) can give electrons (reduce) any of the ions below it.

Cd2+ can (oxidize) gain electrons from the elements above.