How Do You Calculate Cell Potentials for Electrochemical Couples?

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SUMMARY

The calculation of cell potentials for the Zn2+/Zn and Ag+/Ag electrochemical couples involves using standard reduction potentials. The standard reduction potential for Zn2+ + 2e- ⇌ Zn is -0.76 V, and for Ag+ + e- ⇌ Ag is +0.80 V. To find the overall cell potential, the zinc half-reaction should not be flipped, as the direction does not affect the potential value. The correct cell potential is calculated as +1.56 V, confirming that the initial approach was correct despite the homework feedback.

PREREQUISITES
  • Understanding of electrochemical cells and half-reactions
  • Familiarity with standard reduction potentials
  • Knowledge of oxidation and reduction processes
  • Basic algebra for combining potentials
NEXT STEPS
  • Study the Nernst equation for calculating cell potentials under non-standard conditions
  • Learn about the significance of standard reduction potentials in electrochemistry
  • Explore the concept of Gibbs free energy in relation to electrochemical reactions
  • Investigate common mistakes in calculating cell potentials and how to avoid them
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Chemistry students, educators, and anyone studying electrochemistry, particularly those focusing on calculating cell potentials and understanding electrochemical reactions.

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Homework Statement



Calculate the potential of a Zn^2+/Zn and Ag^1+/Ag couple.

Homework Equations



Zn^2+ + 2e^1– ⇌ Zn E= –0.76 V
Ag^1+ + e^1– ⇌ Ag E= +0.80 V

The Attempt at a Solution



First I know to multiply the silver half reaction by two so that each half reaction has two electrons. Then I flip the zinc reaction and switch the sign of its energy. Then, I added the two energies to get a cell potential of 1.56V. However, my homework is telling me that this is incorrect. I can not think of any reason why that is so. Any suggestions? Any help would be much appreciated.
 
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E is not energy. You don't need to balance reaction to calculate potential. You don't flip the reaction - direction doesn't matter, both oxidation and reduction are both taking place at exactly the same potential.

All that being said, 1.56 looks fine to me... I can be missing something - it happens, especiall early in the morning - but I think it is OK.

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