Engineering Chemistry - Unit 3

Van Shot Video Lecture

• Lecture Presenter: Neeraj Tomar
• Unit 3: Electrochemistry
• Today's Target: Complete Unit 3

Electrochemistry

• Definition: A branch of chemistry that studies the conversion of chemical energy to electrical energy and vice versa.
• Cells: Devices that convert chemical energy to electrical energy and back.
  • Two Types:
    • Electrochemical Cell
    • Electrolytic Cell

Differences Between Electrochemical and Electrolytic Cells

• Electrochemical Cell: Converts chemical energy to electrical energy.
• Electrolytic Cell: Converts electrical energy to chemical energy.
• Redox Reaction:
  • Spontaneous redox reactions occur in electrochemical cells.
  • Non-spontaneous redox reactions occur in electrolytic cells, requiring electrical energy.
• Electrodes: Electrochemical cells have different metals, while electrolytic cells have similar or dissimilar electrodes.
• Electrolyte: Electrodes are dipped in an electrolytic solution.
• Salt Bridge: Used in electrochemical cells but not in electrolytic cells.
• Examples:
  • Electrochemical Cell: Galvanic Cell
  • Electrolytic Cell: Lead Acid Storage Battery

Working of Electrochemical Cell

• Diagram: Zinc metal and copper metal electrodes, use of a salt bridge.
• Electron Movement:
  • From anode to cathode.
• Redox Reactions:
  • At the anode: Zinc -> Zinc ions + Electrons.
  • At the cathode: Copper ions + Electrons -> Copper.
• Complete Cell Reaction: Sum of half-cell reactions.

Electromotive Force (EMF)

• Definition: The voltage measured when there is no or negligible current flow in the cell.
• Formula: e0 Cathode - e0 Anode

Corrosion

• Definition of Corrosion: Gradual deterioration of metal due to chemical or electrochemical attacks.
• Factors:​
  • Nature of the metal.
  • Nature of the environment.
    • Galvanic series.
    • Area of anode and cathode.
    • Purity of metal.
    • Effect of temperature and humidity.

Types of Corrosion

1. Dry Corrosion: Occurs in the absence of electrochemical attacks.
2. Wet Corrosion: Occurs in the presence of electrochemical attacks.

Corrosion Prevention Methods

1. Proper Design Utilization
2. Insulation
3. Use of Inhibitors
4. Sacrificial Protection
5. Impressed Current Protection
6. Selection of Proper Material

Cement

• Composition: Calcium Oxide (52-60%), Silica (22-25%), Alumina (5-10%), etc.
• Manufacturing Process:​
  • Mixing (Dry and Wet Process)
  • Burning
  • Grinding
  • Packing
• Initial and Final Setting
  • Reaction with third, fourth, first, and second clinkers.
  • Role of Gypsum: Retards the initial setting

I hope you have understood the complete Unit 3. Thank you so much