Electrolysis and Batteries
Faraday's laws, primary and secondary cells, fuel cells and corrosion. (Chemistry › Electrochemistry, NEET UG syllabus.)
What is Electrolysis and Batteries?
The process of using electrical energy to drive non-spontaneous chemical reactions in an electrolytic cell.
Key formula / rule: Faraday's First Law of Electrolysis
Key points
- Define electrolysis and state Faraday's laws.
- Calculate the amount of substance deposited/liberated during electrolysis.
- Differentiate between primary and secondary cells with examples.
- Describe the working principles of dry cells, lead-acid batteries, and fuel cells.
Common exam trap
Confusing anode/cathode polarity between electrolytic and galvanic cells.
Definitions
- Term
Electrolysis
- Meaning
The process of using electrical energy to drive non-spontaneous chemical reactions in an electrolytic cell.
- Term
Electrolytic Cell
- Meaning
An electrochemical cell that converts electrical energy into chemical energy by driving a non-spontaneous redox reaction.
- Term
Galvanic Cell (Voltaic Cell)
- Meaning
An electrochemical cell that converts chemical energy into electrical energy through a spontaneous redox reaction.
- Term
Primary Cell
- Meaning
A non-rechargeable battery where the electrode reactions are irreversible, and the reactants are consumed during discharge.
- Term
Secondary Cell
- Meaning
A rechargeable battery where the electrode reactions can be reversed by passing an external current, allowing it to be recharged.
- Term
Fuel Cell
- Meaning
A galvanic cell that continuously converts the chemical energy of a fuel (e.g., H₂, CH₄) and an oxidant (e.g., O₂) into electrical energy.
- Term
Corrosion
- Meaning
An electrochemical process involving the gradual deterioration of metals due to their reaction with the environment, typically oxygen and moisture.
- Term
Faraday's Constant (F)
- Meaning
The charge carried by one mole of electrons, approximately 96487 Coulombs per mole (C/mol).
Learning objectives
Define electrolysis and state Faraday's laws.
Calculate the amount of substance deposited/liberated during electrolysis.
Differentiate between primary and secondary cells with examples.
Describe the working principles of dry cells, lead-acid batteries, and fuel cells.
Explain the mechanism of corrosion and methods for its prevention.
Formulae
- Name
Faraday's First Law of Electrolysis
- Note
W is mass deposited/liberated, Z is electrochemical equivalent, I is current, t is time.
- Expression
W = ZIt
- Name
Electrochemical Equivalent (Z)
- Note
E is equivalent weight, F is Faraday's constant (96487 C/mol).
- Expression
Z = E/F
- Name
Mass deposited using Equivalent Weight
- Note
Combines first law with Z definition. E = Molar mass / n-factor.
- Expression
W = (E × I × t) / F
- Name
Faraday's Second Law of Electrolysis
- Note
When the same quantity of electricity is passed through different electrolytes, the masses (W) of substances deposited/liberated are proportional to their equivalent weights (E).
- Expression
W₁/W₂ = E₁/E₂
- Name
Charge (Q)
- Note
Q is total charge in Coulombs, I is current in Amperes, t is time in seconds.
- Expression
Q = I × t
Prerequisites
Basic concepts of oxidation and reduction (redox reactions).
Understanding of electrochemical cells (galvanic cells).
Knowledge of stoichiometry and mole concept.
Ability to balance chemical equations.
Common mistakes
Confusing anode/cathode polarity between electrolytic and galvanic cells.
Incorrectly applying Faraday's laws, especially with equivalent weight calculations.
Not balancing redox reactions correctly for electrode processes.
Misunderstanding the difference between primary and secondary cells.
Forgetting that corrosion is an electrochemical process.
Keywords
Electrolysis
Faraday's Laws
Batteries
Primary Cell
Secondary Cell
Fuel Cell
Corrosion
Dry Cell
Lead-acid battery
Ni-Cd cell
H₂-O₂ fuel cell
Electroplating
Anode
Cathode
Redox
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