Determine the order of reducing agents (strongest to weakest).
A) Mn(s) > Zn(s) > Cr(s) > Fe(s)
B) Fe(s) > Cr(s) > Zn(s) > Mn(s)
C) Mn(s) > Fe(s) > Cr(s) > Zn(s)
D) Zn(s) > Mn(s) > Cr(s) > Fe(s)
I know the half reaction for the following:
- Mn(s) ==> Mn^2+(aq) + 2e-
- Zn(s) ==> Zn^2+(aq) + 2e-
- Cr(s) ==> Cr^3+(aq) + 3e-
- Fe(s) ==> Fe^2+(aq) + 2e-
I am not really sure how to tell which one is stronger than the other.
look at a table of reduction potentials....
http://www.chemeddl.org/services/moodle/media/QBank/GenChem/Tables/EStandardTable.htm
So the one with lowest value is the strongest? Ex: Mn(s) is -1.18
To determine the order of reducing agents (strongest to weakest), we need to consider their reduction potentials. The higher the reduction potential, the stronger the reducing agent.
Looking at the half-reactions you provided:
- Mn(s) ==> Mn^2+(aq) + 2e- (reduction potential: unknown)
- Zn(s) ==> Zn^2+(aq) + 2e- (reduction potential: unknown)
- Cr(s) ==> Cr^3+(aq) + 3e- (reduction potential: unknown)
- Fe(s) ==> Fe^2+(aq) + 2e- (reduction potential: unknown)
Since the reduction potentials are unknown, we need to consult a table of standard reduction potentials. This table usually ranks the elements/compounds in decreasing order of their reduction potentials.
By consulting such a table, we can determine the following standard reduction potentials (E°):
- Mn^2+(aq) + 2e- ==> Mn(s) E° = -1.18 V
- Zn^2+(aq) + 2e- ==> Zn(s) E° = -0.76 V
- Cr^3+(aq) + 3e- ==> Cr(s) E° = -0.74 V
- Fe^2+(aq) + 2e- ==> Fe(s) E° = -0.44 V
Based on these values, we can order the reducing agents from strongest to weakest:
B) Fe(s) > Cr(s) > Zn(s) > Mn(s)
Therefore, option B is the correct order of reducing agents, with Fe(s) being the strongest reducing agent and Mn(s) being the weakest reducing agent.