Electrochemistry: Conductance, Cells, Batteries

Jul 11, 2024

Electrochemistry (NCRT Wala Winner Series)

Introduction

  • Speaker: Shara Grover
  • Subject: Electrochemistry (Winner Series)
  • Objective: Improvement in preparation and high performance

Key Lines

  • Poem on the importance of time: "Each moment is very precious, do not waste it"
  • Motivation: Never stop, face difficulties

Chapter Guidelines

  • Divided into three parts: Conductance, Electrochemical Cell, Batteries
  • Exam Pattern: MCQs, Very Short Questions, Long Questions, Case Based Questions
  • Marking Scheme: CBSE and other boards

Division of Notable Topics

  1. Conductance: Conductance, Types of Conductors, Resistance
  2. Electrochemical Cell: Galvanic and Electrolytic Cell
  3. Batteries and Commercial Cells: Types of Batteries, Corrosion

Conductance

Introduction

  • Ease of charge flow; Resistance: obstruction to charge flow

Types of Conductance

  1. Metallic Conductance: Movement of electrons
  2. Electrolytic Conductance: Movement of ions

Factors Affecting Conductance

  • Nature of Electrolyte: Effect of strong/weak electrolyte
  • Density/Concentration: Effect of dilution
  • Temperature: Increasing temperature increases dissociation and conductance in electrolytes
  • Size of Ion: Conductance decreases with increase in size

Units of Resistance and Conductance

  • Resistance: Ohm (Ω)
  • Conductance: Siemens (S) = Ohm^-1
  • Conductivity: S.cm^-1

Other Important Formulas

  • Conductivity (κ) = G* (L/A)
  • G = C/R (Cell Constant)

Calculation of Conductance

  • Specific Conductance (κ): Specifically for 1 cm^3 volume, G = 1/ρ (resistivity)

Electrochemical Cell (Galvanic Cell/Voltaic Cell)

Introduction

  • Definition: A device that converts chemical energy into electrical energy
  • Example: Daniel Cell

Representation

  • Anode = Oxidation, Cathode = Reduction
  • Outer Circuit: Electrons move from anode to cathode
  • Inner Circuit: Electrons move from cathode to anode

Graphical Example and Representation

  • Output: Seating Terminal, Separation: Salt Bridge
  • Connection of Zinc Electrode, Copper Sulfate, Salt Bridge
  • Main Cell Reaction: Zn + Cu^2+ -> Zn^2+ + Cu

Cell Potential EMF

  • Nernst Equation: E = E^0 - (0.059/n) log C_pr/C_react
  • Electrode Potential (E^0): Measurement Unit: Volt
  • Delta G = -nFE^0, Standard Gibbs Free Energy

Batteries and Commercial Cells

Introduction

  • Medium: Used in daily life

Types

  1. Primary Batteries: Cannot be recharged (e.g. Dry Cell, Mercury Cell)
  2. Secondary Batteries: Can be recharged (e.g. Lead Acid Battery, Nickel Cadmium Battery)

Important Cell Examples

Dry Cell

  • Electrolytes: Ammonium Chloride, Zinc, Maximum EMF: 1.5 Volt

Lead-Acid Battery

  • Electrolytes: Sulfuric Acid, Anode: Lead, Cathode: Lead Dioxide

Fuel Cells

  • Heat and Electrical Energy: High Efficiency, Oxygen and Hydrogen Cell Reactions

Corrosion

  • Reaction of iron and oxygen, process of rusting
  • Prevention Methods: Painting, Electroplating, Sacrificial Protection and Galvanization

Key Conclusion

  • Revision and Practice: DPP and Practice Sheets
  • Next Session: Chemical Kinetics, Questions in Physical Chemistry, Homework Discussion

Homework

  • Given case-based and assertion-reason questions, to be discussed before Physical Chemistry Chemical Kinetics
  • Cheat Sheet and Formula Sheet: Will be provided in PDF