SAT Chemistry

Answer: E. Solution is as follows:

The short hand reaction Zn|Zn⁺² yields a half-reaction of Zn -> Zn⁺² + 2 e^-. This is an oxidation reaction because the zinc’s charge increases and it loses electrons. The corresponding half reaction for copper is Cu⁺² + 2 e^- -> Cu, which is a reduction reaction. The total reaction happening in this cell is:

Zn + Cu⁺² --> Zn⁺² + Cu

Use the equation E_cell° = E_oxidation° + E_reduction°

Look up the standard reduction potential (V) for both half reactions.

Zn --> Zn⁺² + 2 e^- has a V = -0.76V
Cu⁺² + 2 e^- --> Cu has a V = 0.34V

Adding those values yields E_cell° = -0.42V