Relative Strengths of Oxidizing and Reducing Agents
metals: lose electrons
and are good reducing
agents.
non-metals: gain
electrons and are good
oxidizing agents.
Brief Activity Series
Strong Reducing Agent.
Strong Oxidizing Agent
Li+(aq) + e-
↔ Li(s)
Li+(aq) + e- → Li(s)
Eo = -3.04 V (non-spontaneous as written)
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)
Zn2+(aq) + 2e- ↔ Zn(s)
Li+(aq) + e- → Li(s)
Eo = -3.04 V (non-spontaneous as written)
Eo = -0.76 V (non-spontaneous as written
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
Zn2+ is acting as an oxidizing agent. Is it a stronger or weaker oxidizing
stronger,less
agent than Li+?
negative
Zn(s) → Zn2+(aq) + 2eEo = +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)?
Mg(s) can reduce Al3+(aq) or Al3+(aq) can oxidize Mg(s).
What about Al3+(aq) and Zn2+(aq)?
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.