Electrochemical Cells Study Notes

Context: Discussion on electrochemical cells, also known as batteries, and their functioning.

Electrochemical Cells:
- Defined as any kind of battery.
- Can be referred to as voltaic cells, galvanic cells, or Danielle cells.
Batteries:
  - Batteries convert chemical energy into electrical energy.
  - Common household items utilize batteries, such as smoke detectors and garage door openers.
  - Car batteries are also a discussion point.

Electrochemical or Voltaic Cells:
- Convert chemical energy to electrical energy.
- Operate on oxidation-reduction (redox) reactions.
Oxidation and Reduction:
- Oxidation: Loss of electrons. Associated with an increase in oxidation number. Occurs at the anode, which is negatively charged.
- Reduction: Gain of electrons. Associated with a decrease in oxidation number. Occurs at the cathode, which is positively charged.
GERD (Gain Electrons Reduction, Lose Electrons Oxidation):
  - Useful mnemonics to remember redox processes:
    - Leo: Lose Electrons Oxidation.
    - Gerd: Gain Electrons Reduction.

Anode and Cathode Configuration:
- The anode is where oxidation occurs and is negatively charged.
- The cathode is where reduction occurs and is positively charged.
Chemical Processes Within a Battery:
- Car batteries change chemical energy to electrical energy when starting the vehicle. An alternator then takes over during driving, switching to a non-spontaneous reaction.

Metallic Electrodes:
  - Electrodes must be metals for functioning.
  - Inside car batteries, sulfuric acid serves as an ion conductor. Concentration of sulfuric acid affects battery life.
  - Salt may be present in household batteries to assist with the migration of ions.
Flow of Electrons:
- Electrons flow through metallic wires in a battery to create current.
- A flow of electrons and migration of ions are essential for battery functioning.

Salt Bridge:
- Conducts ions to maintain electrical neutrality in the battery.
- Prevents mixing of the oxidation and reduction reactions which can lead to battery failure.

Purpose of Voltaic Cells:
- Convert chemical energy into electrical energy, which results in the generation of voltage.
- A spontaneous reaction results in a positive voltage, indicating that current is being produced.
Standard Reduction Table:
  - Used to determine voltages associated with specific half-cell reactions.
  - For example:
    - Oxidation of potassium ( $K^0 <br>ightarrow K^{+1} + e^-$ ) has +2.93 V when inverted from reduction to oxidation.
    - Reduction of nickel ( $Ni^{+2} + 2e^- <br>ightarrow Ni^0$ ) has -0.26 V.

Construction of Danielle Cells:
  - Requires two metals and their respective ions.
  - For example, zinc and copper metals must be paired with their respective zinc sulfate and copper sulfate solutions.
  - Current flow is supported by both the flow of electrons and migration of ions through the salt bridge.

Oxidation and Reduction in Specific Reactions:
  - At the anode, zinc will oxidize releasing electrons,
     $Zn^0 <br>ightarrow Zn^{+2} + 2e^-$ ;
  - At the cathode, copper will reduce, consuming electrons,
     $Cu^{+2} + 2e^- <br>ightarrow Cu^0$ .
Direction of Electron Flow:
- Electrons flow from the anode (oxidation site) to the cathode (reduction site).

Understanding Basic Functions of Electrochemical Cells:
  - It's essential to grasp concepts of oxidation and reduction and how they reflect in battery formation.
  - Students are encouraged to memorize the terms related to anodes, cathodes, and the associated reactions.
  - The homework focus includes reviewing concepts related to the last class and preparing for upcoming assessments.