Sel Elektrokimia (1) | Sel Volta Dan Sel Elektrolisis | Rangkaian Sel

Main ideas / lessons conveyed

• The video introduces electrochemical cells and explains how they relate to redox (oxidation–reduction) reactions.
• It contrasts two types of electrochemical cells:
  • Voltaic (galvanic) cells: convert chemical energy → electrical energy using spontaneous redox reactions.
  • Electrolytic cells: use electrical energy → chemical energy to drive non-spontaneous redox reactions.

Key concepts explained

1) What is an electrochemical cell?

An electrochemical cell is a device that can:

• Produce electrical energy/current from chemical reactions (redox), or
• Use electrical energy to carry out chemical reactions (redox).

2) Two types of electrochemical cells

• Voltaic cell

  • Produces electrical current because the redox reaction is spontaneous
  • Chemical energy → electrical energy

• Electrolytic cell

  • Requires an external power source because the redox reaction is not spontaneous
  • Electrical energy → chemical energy

Similarities between voltaic and electrolytic cells

• Both use two electrodes:
  • Cathode: where reduction occurs
  • Anode: where oxidation occurs
  • Mnemonics:
    • “Katod = reduction (cathode reduction)”
    • “Anod = oxidation (anode oxidation)”
• Both use electrolytes:
  • Can be an aqueous solution, a melt, or another liquid form.

Differences between voltaic and electrolytic cells

1) Energy conversion direction

• Voltaic: chemical energy → electrical energy
• Electrolytic: electrical energy → chemical energy

2) Polarity of electrodes (as described)

• Voltaic cell

  • Cathode = positive pole
  • Anode = negative pole
  • Mnemonic: “Kapan volta”

• Electrolytic cell

  • Cathode = negative pole
  • Anode = positive pole
  • Mnemonic: “Wah”

3) Spontaneity and sign of cell potential

• Voltaic cell

  • Spontaneous
  • E°cell > 0 (positive)

• Electrolytic cell

  • Not spontaneous
  • E°cell < 0 (negative or described as “small from zero or negative”)

4) Everyday applications

• Voltaic cells: batteries
• Electrolytic cells: metal plating and refining

How the cell circuits work (step-by-step)

A) Voltaic cell circuit (as explained)

The cell is split into two half-cells:

• One container for the oxidation half-reaction
• One container for the reduction half-reaction

Each half-cell contains:

• an electrode
• an electrolyte solution

Example composition given

• Left half-cell: ZnSO₄ solution with Zn²⁺ and SO₄²⁻
• Right half-cell: CuSO₄ solution with Cu²⁺ and SO₄²⁻

Electrode roles in the example

• Zn electrode = anode (negative pole)
• Cu electrode = cathode (positive pole)

Connections

• Electrodes are connected via an external circuit (a conductor wire + voltmeter).
• The voltmeter measures the voltage produced by the redox reaction.

Working principle (voltaic cell)

• At the anode (Zn oxidation):
  • Zn releases electrons (conceptually):
    • Zn → Zn²⁺ + 2e⁻
• Electron flow:
  • Electrons travel through the wire to the cathode
• At the cathode (Cu²⁺ reduction):
  • Cu²⁺ captures electrons to form Cu metal (conceptually):
    • Cu²⁺ + 2e⁻ → Cu(s)

Ion balance via internal circuit (salt bridge)

• A salt bridge (inverted-U tube) contains salt such as KCl (K⁺ and Cl⁻ ions).
• K⁺ moves toward the cathode to neutralize excess negative/imbalance near sulfate.
• Cl⁻ moves toward the anode to neutralize excess Zn²⁺ charge.
• This maintains charge neutrality so the reaction continues.

Result

• Continuous electron flow (anode → cathode) produces electric current.

B) Electrolytic cell circuit (as explained)

The cell is designed in one container containing:

• an electrolyte
• two electrodes

Electrodes are connected to a DC power supply:

• electrode connected to the positive terminal = anode
• electrode connected to the negative terminal = cathode

Ion movement and reactions (as described)

• At cathode (negative electrode):
  • Positive ions migrate to cathode
  • Reduction occurs
• At anode (positive electrode):
  • Negative ions migrate to anode
  • Oxidation occurs
• Electrons produced during oxidation are returned to the positive terminal through the power source.

Key takeaway

• The overall reaction is not spontaneous, so it requires electrical energy input.
• The video notes that further details about electrolysis are planned for a later section.

Speakers / sources featured

• Brother (host/presenter) on the Kinematics channel (referred to as “Brother on the kinematics channel”).