To determine which species is the least likely to be reduced, we need to consider their standard reduction potentials. The standard reduction potential (E°) indicates the tendency of a species to gain electrons and be reduced. The more positive the reduction potential, the greater the species' tendency to be reduced.
Here are the standard reduction potentials for the given species:
- [tex]\( Zn^{2+} + 2e^- \rightarrow Zn \quad E° = -0.76 \, V \)[/tex]
- [tex]\( Fe^{3+} + 3e^- \rightarrow Fe \quad E° = -0.04 \, V \)[/tex]
- [tex]\( Cu^{2+} + 2e^- \rightarrow Cu \quad E° = 0.34 \, V \)[/tex]
- [tex]\( Fe^{2+} + 2e^- \rightarrow Fe \quad E° = -0.44 \, V \)[/tex]
The species with the lowest (most negative) standard reduction potential is the least likely to be reduced. Here's a comparison of the reduction potentials:
1. [tex]\( Zn^{2+} \)[/tex] has a reduction potential of [tex]\( -0.76 \, V \)[/tex].
2. [tex]\( Fe^{2+} \)[/tex] has a reduction potential of [tex]\( -0.44 \, V \)[/tex].
3. [tex]\( Fe^{3+} \)[/tex] has a reduction potential of [tex]\( -0.04 \, V \)[/tex].
4. [tex]\( Cu^{2+} \)[/tex] has a reduction potential of [tex]\( 0.34 \, V \)[/tex].
Among these:
- [tex]\( Zn^{2+} \)[/tex] has the most negative reduction potential at [tex]\( -0.76 \, V \)[/tex].
- [tex]\( Fe^{2+} \)[/tex] follows with [tex]\( -0.44 \, V \)[/tex].
- [tex]\( Fe^{3+} \)[/tex] has [tex]\( -0.04 \, V \)[/tex].
- [tex]\( Cu^{2+} \)[/tex] has the highest (most positive) reduction potential at [tex]\( 0.34 \, V \)[/tex].
Since [tex]\( Zn^{2+} \)[/tex] has the most negative standard reduction potential among the given options, it is the least likely to be reduced.
Therefore, the species least likely to be reduced is:
A. [tex]\( Zn^{2+} \)[/tex]
