Physical chemistryLesson 2 of 4 in the course Electrochemistry

Electrode Potentials, the SHE, and Cell Spontaneity

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces electrical potential as a way to quantify the driving force for electron transfer in redox reactions. It explains why a single electrode's potential cannot be measured by itself and how a complete electrochemical cell provides a measurable cell potential.

In a redox reaction, electrons move from a reductant (electron donor) to an oxidant (electron acceptor). The potential associated with this transfer reflects its driving force. In electrical applications, potential is commonly called voltage.

All flashcards

Why is the standard hydrogen electrode (SHE) assigned a potential of 0 V?
It is a reference convention that allows other standard electrode potentials to be measured relative to it.
What is a standard electrode potential?
The potential of a half-cell measured under standard-state conditions relative to a reference electrode; it is tabulated for reduction.
How does reversing a half-reaction affect its electrode potential?
It changes the sign of the potential.
Does multiplying a half-reaction to balance electrons change its electrode potential?
No. Electrode potential is an intensive property and is not multiplied by reaction coefficients.
What does a positive standard cell potential indicate?
The specified reaction direction is thermodynamically spontaneous under standard-state conditions; it does not specify the reaction rate.

Quiz questions

  1. What is the standard potential assigned to the standard hydrogen electrode?Answer: Exactly 0 V by convention.
  2. In the standard hydrogen electrode, what role does platinum serve?Answer: It provides a conductive surface for electron transfer without being consumed.
  3. Which species is the stronger oxidizing agent under standard conditions: Ag⁺ or Pb²⁺? The standard reduction potentials are +0.7996 V for Ag⁺/Ag and −0.1262 V for Pb²⁺/Pb.Answer: Ag⁺, because its reduction potential is more positive.
  4. For the reaction Cu(s) + 2Ag⁺(aq) → Cu²⁺(aq) + 2Ag(s), use E°(Ag⁺/Ag) = +0.7996 V and E°(Cu²⁺/Cu) = +0.34 V. What is E°cell?Answer: Approximately +0.46 V.
  5. What happens to the cell potential when the overall cell reaction is reversed?Answer: Its sign changes to the opposite sign.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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