Understanding Redox Chemistry Concepts

Sep 3, 2024

Lecture on Redox Chemistry

Overview

  • Focus on Redox (Reduction-Oxidation) reactions.
  • Review of oxidation numbers and rules.
  • Discussion on identifying redox reactions.
  • Importance of electron transfer in redox.
  • Methods for balancing redox reactions: Half-reaction method and PA FU method.

Oxidation Numbers

  • Key rules:
    1. Pure elements have an oxidation number of zero.
    2. Oxygen is usually -2 (except in peroxides where it is -1).
    3. Hydrogen is +1 in compounds.
    4. The sum of oxidation numbers equals the charge on the entity.
  • Example calculations of oxidation states for compounds like CO2, Iodate, and Peroxides.

Identifying Redox Reactions

  • Redox reactions involve electron transfer.
  • Oxidation: loss of electrons.
  • Reduction: gain of electrons.
  • Use of oxidation numbers to identify changes.
  • Examples:
    • NH3 to N in NH4+
    • Identifying whether reactions are redox or not.

Balancing Redox Reactions

Half-Reaction Method

  • Separate reactions into half-reactions.
  • Balance atoms other than H and O first.
  • Balance O using water, balance H using H+ ions, and finally balance charges with electrons.
  • Example: Balancing reactions involving Selenium and Permanganate.

PA FU Method

  • Focuses on oxidation numbers.
  • Calculate changes in oxidation numbers to find electron transfer.
  • Use lowest common multiple of electrons to balance.

Spontaneity of Reactions

  • Spontaneous reactions occur naturally, non-spontaneous do not.
  • Spontaneous reactions have a positive voltage.
  • Use tables of half-reactions to determine spontaneity.
  • Examples:
    • Bromine and Lead reaction.
    • Nickel and Copper reaction.

Major Entities and Reaction Predictions

  • Disassociation of ionic compounds and strong acids in water.
  • Identifying strongest oxidizing and reducing agents.
  • Predicting reactions based on the strongest agents.

Disproportionation Reactions

  • A single substance is both oxidized and reduced.
  • Examples highlighted.

Tables of Half-Reactions

  • Oxidizing agents on the left, reducing agents on the right.
  • Strongest oxidizing agent is top left, strongest reducing agent is bottom right.

Titrations

  • Not always acid-base, can be redox titrations.
  • Importance of consistent titration volume measurements.
  • Example of trial evaluation.

Next Steps

  • Review upcoming topics: Organic chemistry test review, titrations, and electrochemical cells.