Reduction Potentials? T/F Statements

Question

Use the following standard reduction potentials to answer the questions below.

(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

Evaluate the following statements and determine if they are True or False.

1) Al (s) can be oxidized by Fe3 (aq).

2) A positive reduction potential means that the metal is more 3) stable in its reduced state (s) than in its ionic state (aq).

4) The reduction potential of iron indicates that iron rusts (forms Fe2O3) spontaneously.

5) Fe3 (aq) can oxidize Al (s).

6) Elemental copper (Cu (s)) is more stable than elemental iron (Fe (s)).

Answer 1

Caitlin I'm glad you posted the potentials this time. Very helpful.  Nobody likes looking up data.

(1) TRUE  (thermite reaction!)

(2) (3)  Huh?  false  You can't comment on stability with a reduction potential ... only complete redox reactions have true thermodynamic quantities associated with them.

(4) False ... that data alone is not enough.  You would have to consider the reduction potential of O2 to oxide also, and besides, Fe2O3 is a solid, whereas all your potential data is in solution, so there would have to be a solubility product constant to consider as well.

(5) Yes that's the same as (1)

(6) No no no ... you can't make assumptions about stability based on single potentials.  Potentials must be combined into redox reactions before you can make thermochemical statements