Consider the following standard reduction potentials of some commonly used metals:
ξo (V)
Au3+ (aq) + 3 e- → Au (s) +1.50
Ag+ (aq) + e- → Ag (s) +0.80
Cu2+ (aq) + 2e- → Cu (s) +0.34
Fe3+ (aq) + 3e- → Fe (s) -0.036V
Al3+ (aq) + 3e- → Al (s) -1.66
Mg2+ (aq) + 2e- → Mg (s) -2.37
Using the reduction potentials one can compare the reactivities of metals towards oxidation- reduction processes. Evaluate the following statements and determine if they are True or False.
1. Cu2+ (aq) can oxidize Fe (s).
2. Aluminum has a strong tendancy to be oxidized and is therefore not a precious metal.
3. A positive reduction potential means that the metal is more stable in its ionic state (aq) than in its reduced state (s).
4. Cu (s) can be oxidized by Au3+ (aq).
5. Elemental copper (Cu (s)) is more stable than elemental iron (Fe (s)).
1. True. According to the reduction potentials, Cu2+ has a higher reduction potential (0.34V) compared to Fe3+ (-0.036V). This means that Cu2+ has a greater tendency to gain electrons and be reduced, while Fe3+ has a greater tendency to lose electrons and be oxidized. Therefore, Cu2+ can oxidize Fe (s).
2. True. The reduction potential of Al3+ (-1.66V) is more negative than the reduction potential of Au3+ (1.50V). This indicates that Al3+ has a higher tendency to lose electrons and be oxidized compared to Au3+. Precious metals like gold (Au) have a lower tendency to be oxidized, making aluminum less precious.
3. False. A positive reduction potential (greater than zero) indicates that the metal ion is more likely to gain electrons and be reduced, while the metal in its elemental form is more stable. In other words, a positive reduction potential means that the metal is more stable in its reduced state (s) than in its ionic state (aq).
4. False. Cu (s) has a reduction potential of 0.00V, while Au3+ has a reduction potential of 1.50V. This means that Au3+ has a greater tendency to be reduced, while Cu (s) has a lower tendency to be oxidized. Therefore, Cu (s) cannot be oxidized by Au3+ (aq).
5. False. The reduction potential of Cu2+ (0.34V) is higher than the reduction potential of Fe3+ (-0.036V). This indicates that Cu2+ has a higher tendency to gain electrons and be reduced compared to Fe3+. Therefore, elemental iron (Fe (s)) is more stable than elemental copper (Cu (s)).
To evaluate the statements and determine if they are true or false, we need to compare the reduction potentials of the metal species involved in each statement.
1. Cu2+ (aq) can oxidize Fe (s):
To determine if Cu2+ (aq) can oxidize Fe (s), we compare their reduction potentials. The reduction potential for Cu2+(aq) + 2e- → Cu(s) is +0.34V, while the reduction potential for Fe3+(aq) + 3e- → Fe(s) is -0.036V.
Since Cu2+ has a higher reduction potential than Fe3+, Cu2+ is more likely to gain electrons and be reduced, while Fe is more likely to lose electrons and be oxidized. Therefore, Cu2+ (aq) can oxidize Fe (s). This statement is True.
2. Aluminum has a strong tendency to be oxidized and is therefore not a precious metal:
To evaluate this statement, we compare the reduction potentials of Al and other precious metals like Au.
The reduction potential for Al3+(aq) + 3e- → Al(s) is -1.66V. Since it has a lower reduction potential compared to Au3+(aq) + 3e- → Au(s) (+1.50V), it means that Al is more likely to be oxidized compared to Au. Therefore, aluminum has a strong tendency to be oxidized and is not considered a precious metal. This statement is True.
3. A positive reduction potential means that the metal is more stable in its ionic state (aq) than in its reduced state (s):
This statement is False. A positive reduction potential means that the metal is more likely to be reduced and become a solid, while a negative reduction potential means that the metal is more likely to be oxidized and become an ion in solution. A positive reduction potential indicates a stronger tendency for reduction, not stability in the ionic state.
4. Cu (s) can be oxidized by Au3+ (aq):
To determine if Cu (s) can be oxidized by Au3+ (aq), we compare their reduction potentials. The reduction potential for Au3+(aq) + 3e- → Au(s) is +1.50V, while Cu2+(aq) + 2e- → Cu(s) is +0.34V.
Since Au3+ has a higher reduction potential than Cu2+, Au3+ is more likely to be reduced while Cu is more likely to be oxidized. Therefore, Cu (s) can be oxidized by Au3+ (aq). This statement is True.
5. Elemental copper (Cu (s)) is more stable than elemental iron (Fe (s)):
To evaluate this statement, we compare the reduction potentials of Cu and Fe. The reduction potential for Cu2+(aq) + 2e- → Cu(s) is +0.34V, while Fe3+(aq) + 3e- → Fe(s) is -0.036V.
Since Cu has a higher reduction potential than Fe, Cu is more likely to gain electrons and be reduced, making it more stable than Fe in its elemental state. Therefore, elemental copper (Cu (s)) is more stable than elemental iron (Fe (s)). This statement is True.