Electrolysis Lecture Notes

Voltaic Cell Overview

Voltaic Cell Functionality:
- Utilizes a spontaneous redox reaction to produce electric current.
- Zinc Electrode Reaction:
  - Solid zinc (Zn) turns into zinc ions (Zn²⁺).
  - Loss of 2 electrons (oxidation) takes place at the zinc electrode (Anode).
  - Anode is negative; mnemonic: "anox" (Anode Oxidation).
- Copper Electrode Reaction:
  - Copper ions (Cu²⁺) gain electrons to form solid copper.
  - Gain of electrons (reduction) occurs at the copper electrode (Cathode).
  - Cathode is positive; mnemonic: "red cat" (Reduction Cathode).
- Reaction Characteristics:
  - Spontaneous reaction.
  - Standard cell potential (E⁰) = +1.10 volts (positive).

Electrolytic Cell Functionality:
- Uses electric current to drive a non-spontaneous redox reaction.
- Reaction Reversal:
  - Involves solid copper and zinc ions.
  - Reverse of voltaic cell reaction.
  - Standard cell potential (E⁰) = -1.10 volts (negative).
- External Voltage Source Required:
  - A battery is needed to drive non-spontaneous reaction.
  - Minimum voltage required is 1.10 volts, often higher in practice.

Zinc Electrode Reaction:
- Electrons forced onto zinc electrode by battery.
- Zinc ions (Zn²⁺) gain electrons (reduction) to form solid zinc.
- Reduction at zinc electrode (Cathode; "red cat").
- Zinc electrode becomes negative due to electron gain.
Copper Electrode Reaction:
- Electrons are pulled away towards battery.
- Solid copper loses electrons to form copper ions (Cu²⁺) (oxidation).
- Oxidation at copper electrode (Anode; "anox").
- Copper electrode loses mass over time.

Voltaic vs. Electrolytic Cells:
- Voltaic cell creates current via spontaneous reaction.
- Electrolytic cell requires current and external voltage source for non-spontaneous reaction.
Electrode Sign Differences:
- Voltaic Anode: Negative; Electrolytic Anode: Positive.
- Voltaic Cathode: Positive; Electrolytic Cathode: Negative.
- Electrolytic cell electrode signs match battery terminal signs.