Electrolysis
Core Concept
Electrolysis is a process that uses an electric current to induce a chemical reaction that would not occur spontaneously.
Key Purpose: Convert electrical energy into chemical energy.
Electrolysis uses electrical energy to drive non-spontaneous reactions.
Reduction occurs at the cathode; oxidation occurs at the anode.
Faraday’s laws relate the amount of substance produced to the current and time.
Applications include metal extraction, electroplating, water splitting, and refining.
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Components of an Electrolytic Cell
Power Source: Provides the electric current necessary to drive the reaction.
Electrodes:
Cathode:
Site of reduction (gain of electrons).
Connected to the negative terminal of the power supply.
Anode:
Site of oxidation (loss of electrons\text{loss of electrons}loss of electrons).
Connected to the positive terminal of the power supply.
Electrolyte: Ionic solution or molten compound that conducts electricity by allowing ions to move.
Key Concepts
Reduction at the Cathode:
Positive ions (cations\text{cations}cations) gain electrons to form neutral atoms.
Example: Na++e−→Na\text{Na}^+ + e^- \rightarrow \text{Na}Na++e−→Na.
Oxidation at the Anode:
Negative ions (anions\text{anions}anions) lose electrons to form neutral atoms or molecules.
Example: 2Cl−→Cl2+2e−2\text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-2Cl−→Cl2+2e−.
Energy Requirement:
Electrolysis requires energy input because the reactions are non-spontaneous.
Faraday’s Laws of Electrolysis
First Law: The mass (m) of a substance produced at an electrode is proportional to the amount of charge (Q) passed through the electrolyte.
m = Z ⋅ Q
Where:
Z: Electrochemical equivalent (g/C).
Q: Charge (C).
Q = I ⋅ t, where I is current (A) and t is time (s).
Second Law: For the same amount of charge, the mass of different substances produced is proportional to their molar masses divided by the number of electrons transferred per ion (n):
$m \propto \frac{M}{n}$