Understanding Redox Chemistry Fundamentals

Sep 3, 2024

Redox Chemistry Lecture

Redox Fundamentals

  • Oxidation Numbers:
    • Elements typically have an oxidation state of zero.
    • Oxidation numbers represent electron distribution in a molecule.
    • In pure elements like chlorine, where electronegativity is equal, the oxidation number is zero.
  • Electronegativity:
    • Chlorine has a high electronegativity of 3.2.
    • Electronegativity affects electron pull in bonds.

Oxidation Number Rules

  • Common Oxidation States:
    • Oxygen in compounds: -2 except in peroxides where it is -1.
    • Hydrogen in compounds: +1.
    • Sum of oxidation numbers equals the charge of the compound.

Identifying Redox Reactions

  • Electron Transfer: Essential for redox reactions.
  • Half-Reactions: Must balance gained and lost electrons.
  • Identifying Redox:
    • Use oxidation numbers to check if they change across reactions.
    • Non-redox: Acid-base reactions and double replacement reactions.

Redox Examples

  • Example 1: NH3 reaction shows no change in oxidation state - not redox.
  • Example 2: Reaction with oxygen changes oxidation state, confirming redox.

Balancing Redox Reactions

  • Half-Reaction Method:
    • Balance non-O and non-H elements first.
    • Balance O with water, balance H with H+.
    • Balance charge with electrons.
  • Example:
    • SN to SN2+ involves losing electrons (oxidation).
    • Permanganate to Mn2+ involves gaining electrons (reduction).

Spontaneity in Redox

  • Spontaneous vs Non-Spontaneous:
    • Determined by potential energy (downhill on the table of half-reactions).
    • Example: Bromine and lead reaction is spontaneous.

Practical Applications

  • Electrochemical Cells:
    • Spontaneous reactions have positive voltages.
    • Strong reducing agents do not spontaneously form stronger reducing agents.

Major Entities in Redox

  • Ionic and Acid Solutions:
    • Ionic compounds and strong acids split in water.
  • Reaction Predictions:
    • Identify strongest oxidizing/reducing agents.
    • Example: Nickel nitrate in iron container.

Titrations and Electrochemistry

  • Redox Titrations:
    • Not all titrations have a neutral equivalence point.
    • Example: Standard solution trials must be consistent within 0.2 mL.

Upcoming Topics

  • Organic Chemistry Review: Scheduled for Monday.
  • Continued Redox Review: Includes titration completion and electrochemical cells.