39. Redox Reactions: Displacement & Ionic Equations

Redox Reactions: Displacement & Ionic Equations

Based on the video, here are the notes on redox reactions, including the use of "OIL RIG," ionic equations, and half equations.

1. Defining Redox

A redox reaction is a reaction where reduction and oxidation both take place at the same time.

• Oxidation: The loss of electrons.

• Reduction: The gain of electrons.

• OIL RIG: A helpful mnemonic standing for Oxidation Is Loss, Reduction Is Gain (of electrons).

2. Displacement as Redox

Displacement reactions, where a more reactive metal replaces a less reactive one, are a common type of redox reaction.

• Example: Adding Calcium to a solution of Iron Sulfate.

  • The Calcium atoms lose electrons to become ions (Oxidation).

  • The Iron ions gain those electrons to become solid metal atoms (Reduction).

3. Ionic Equations

Ionic equations focus only on the particles that change during a reaction.

• Spectator Ions: Ions that do not change or participate in the exchange of electrons (e.g., the sulfate ion in the calcium/iron example). These are removed to simplify the equation.

• Simplified Ionic Equation: Ca + Fe²⁺ → Ca²⁺ + Fe.

4. Half Equations

Half equations show what happens to each individual element in terms of electron gain or loss.

• Oxidation Half Equation (Calcium): Ca → Ca²⁺ + 2e⁻.

  • The electrons are written on the right because they are being "lost" or produced.

• Reduction Half Equation (Iron): Fe²⁺ + 2e⁻ → Fe.

  • The electrons are written on the left because they are being "gained" or added to the ion.

• Tip: Always ensure the total charge on the left side of the arrow equals the total charge on the right side.