Concept explainers
Consider the addition of the following half-reactions:
(1)
(2)
(3)
Because half-reactions (1) and (2) contain a different number of electrons, the net reaction (3) is another half-reaction, and E°3 can’t be obtained simply by adding E°1 and E°2. The free-energy changes, however, are additive because G is a state function:
- (a) Starting with the relationship between Δ G° and E°, derive a general equation that relates the E° values for half-reactions (1), (2), and (3).
- (b) Calculate the value of E°3 for the Fe3+/Fe2+ half-reaction.
- (c) Explain why the E° values would be additive (E°3 = E°1 + E°2) if reaction (3) were an overall cell reaction rather than a half-reaction.
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General Chemistry: Atoms First
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