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Electrochemical (Galvanic) Cell Flashcards

Learn the fundamentals of electrochemical (galvanic) cells, including definitions, half‑reactions, cell notation, potentials, and the role of the salt bridge.

20 cards~7 min
Electrochemical (Galvanic) Cell Flashcards — Qwi
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1What is an electrochemical cell?
Answer

A device that converts chemical energy to electrical energy via redox reactions

It uses oxidation and reduction reactions to generate a flow of electrons, producing electric current.
2What is another name for a galvanic cell?
Answer

Voltaic cell

3In the Daniell cell, the anode is the {{zinc electrode}} where oxidation occurs.
Answer

zinc electrode

4The cathode in a Daniell cell is the {{copper electrode}} where reduction occurs.
Answer

copper electrode

5Electrons flow from the copper electrode to the zinc electrode in a Daniell cell.
Answer

False

Electrons travel from zinc (anode) to copper (cathode).
6Difference between oxidation electrode potential and reduction electrode potential?
Answer

Oxidation → tendency to lose electrons | Reduction → tendency to gain electrons

7Write the oxidation half-reaction for the zinc electrode in a Daniell cell.
Answer

Zn(s) → Zn^{2+}(aq) + 2e−

Zinc metal loses two electrons becoming Zn^{2+} ions.
8Write the reduction half-reaction for the copper electrode in a Daniell cell.
Answer

Cu^{2+}(aq) + 2e− → Cu(s)

Copper ions gain electrons to form solid copper.
9The overall cell reaction for the Daniell cell is {{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)}}.
Answer

Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)

10The salt bridge allows the two electrolyte solutions to mix directly.
Answer

False

It permits ion flow while preventing direct mixing of the solutions.
11What is the main function of the salt bridge in a galvanic cell?
Answer

Maintains electrical neutrality by allowing ion migration

It balances charge buildup, completing the circuit without mixing solutions.
12In cell notation, a single vertical line (|) represents the {{boundary between a metal electrode and its electrolyte solution}}.
Answer

boundary between a metal electrode and its electrolyte solution

13According to convention, which half-cell is written on the left side in cell notation?
Answer

The oxidation (anode) half-cell

The left side denotes the anode where oxidation occurs.
14All electrode potentials are expressed as oxidation potentials by modern convention.
Answer

False

They are expressed as reduction potentials.
15Standard reduction potentials of Zn and Cu?
Answer

Zn: -0.76 V | Cu: +0.34 V

Zn has a negative potential indicating it tends to oxidize; Cu has a positive potential indicating reduction.
16What is the standard cell potential of the Daniell cell?
Answer

1.10 V

Calculated as E_cathode - E_anode = 0.34 - (-0.76) = 1.10 V.
17Increasing the concentration of Zn^{2+} ions in solution increases the electrode potential of the zinc electrode.
Answer

False

Higher Zn^{2+} shifts equilibrium left, decreasing the electrode potential.
18How does temperature affect electrode potential?
Answer

It changes equilibrium and reaction rates, altering the potential

Higher or lower temperature modifies the electrochemical reaction rate, thus affecting the electrode potential.
19The relationship between oxidation and reduction potentials for the same electrode is {{E_{ox} = -E_{red}}}.
Answer

E_{ox} = -E_{red}

20A higher oxidation potential indicates a greater tendency to gain electrons.
Answer

False

Higher oxidation potential means a greater tendency to lose electrons.

Electrochemical (Galvanic) Cells: Fundamentals

An electrochemical cell is a device that converts chemical energy into electrical energy through redox (reduction‑oxidation) reactions. In a galvanic, or voltaic, cell the spontaneous redox reaction drives a flow of electrons through an external circuit, producing an electric current.

Key Terminology

  • Oxidation: loss of electrons; occurs at the anode.
  • Reduction: gain of electrons; occurs at the cathode.
  • Electrode potential: a measure of the tendency of a species to be reduced (or oxidized) under standard conditions.
  • Salt bridge: a pathway that allows ion migration to maintain electrical neutrality without mixing the two electrolyte solutions directly.

Daniell Cell Example

The Daniell cell is a classic galvanic cell consisting of a zinc electrode immersed in a ZnSO₄ solution and a copper electrode immersed in a CuSO₄ solution. The cell components are arranged as follows:

  • Anode (oxidation site): zinc electrode (Zn(s)).
  • Cathode (reduction site): copper electrode (Cu(s)).

Electrons travel from the zinc electrode to the copper electrode through the external circuit, while ions move through the salt bridge to preserve charge balance.

Half‑Reactions

Writing the half‑reactions clarifies the electron flow:

  • Oxidation (zinc side): Zn(s) → Zn²⁺(aq) + 2e⁻
  • Reduction (copper side): Cu²⁺(aq) + 2e⁻ → Cu(s)

Combining these yields the overall cell reaction:

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Cell Notation

Cell notation compactly represents the components of a galvanic cell. A single vertical line (|) denotes the boundary between a metal electrode and its electrolyte solution. By convention, the oxidation half‑cell is written on the left, the reduction half‑cell on the right, and a double vertical line (||) separates the two half‑cells, representing the salt bridge.

For the Daniell cell the notation is:

Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s)

Standard Electrode Potentials

Standard reduction potentials (E°) are measured under standard conditions (1 M concentration, 25 °C, 1 atm). For the relevant electrodes:

  • Zn²⁺ + 2e⁻ → Zn(s) E° = –0.76 V
  • Cu²⁺ + 2e⁻ → Cu(s) E° = +0.34 V

Modern convention expresses all potentials as reduction potentials. The oxidation potential of a given electrode is simply the negative of its reduction potential (Eₒₓ = –Eᵣₑd).

Cell Potential Calculation

The standard cell potential (E°cell) is obtained by subtracting the anode potential from the cathode potential:

E°cell = E°cathode – E°anode = 0.34 V – (–0.76 V) = 1.10 V

This positive value confirms that the Daniell cell reaction is spontaneous.

Influence of Concentration and Temperature

Changing the concentration of ions alters the electrode potentials according to the Nernst equation. Increasing Zn²⁺ concentration actually lowers the zinc electrode potential because the reaction shifts toward the left, reducing the driving force for oxidation.

Temperature also affects potentials by modifying equilibrium constants and reaction rates. Higher temperatures can either increase or decrease the cell potential depending on the enthalpy change of the redox reaction.

Role of the Salt Bridge

The salt bridge maintains electrical neutrality by allowing the migration of ions. It does not permit the two electrolyte solutions to mix directly; instead, it provides a conductive pathway that balances charge buildup, ensuring continuous electron flow through the external circuit.

Common Misconceptions

  • Electrons flow from copper to zinc in a Daniell cell – False. Electrons travel from zinc (anode) to copper (cathode).
  • The salt bridge mixes the two solutions – False. It only allows ion migration while keeping the solutions separate.
  • All electrode potentials are expressed as oxidation potentials – False. They are reported as reduction potentials by convention.
  • A higher oxidation potential means a greater tendency to gain electrons – False. It indicates a greater tendency to lose electrons.

Summary

Electrochemical (galvanic) cells harness spontaneous redox reactions to generate electrical energy. The Daniell cell illustrates core concepts: oxidation at the zinc anode, reduction at the copper cathode, electron flow through an external circuit, and ion flow through a salt bridge to preserve charge balance. Understanding half‑reactions, cell notation, and electrode potentials enables prediction of cell behavior and calculation of the cell voltage, essential skills in chemistry and electrochemistry.