Balancing Redox Reactions

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Topic Summary & Highlights
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Core Concept

Redox (reduction-oxidation) reactions involve the transfer of electrons between chemical species.

  • Key Processes:

    • Oxidation: Loss of electrons (LEO:Loss of Electrons is Oxidation\text{LEO}: \text{Loss of Electrons is Oxidation}LEO:Loss of Electrons is Oxidation).

    • Reduction: Gain of electrons (GER:Gain of Electrons is Reduction\text{GER}: \text{Gain of Electrons is Reduction}GER:Gain of Electrons is Reduction).

Practice Tips

  • Practice Systematic Steps: Follow the process step by step to avoid errors.

  • Check Your Work: Ensure both mass and charge are balanced.

  • Redox reactions are split into oxidation and reduction half-reactions.

  • Use $\text{H}^+$, $\text{OH}^−$, and $\text{H}_2\text{O}$ to balance atoms in acidic or basic solutions.

  • Electrons must balance between the two half-reactions.

  • Practice makes perfect—balancing redox reactions becomes easier with repetition.

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Steps to Balance Redox Reactions

Step 1: Split the Reaction into Half-Reactions

  • Identify the species that are oxidized and reduced.

  • Write the oxidation half-reaction (showing loss of electrons).

  • Write the reduction half-reaction (showing gain of electrons).

Step 2: Balance Each Half-Reaction

  1. Balance Elements Other Than Oxygen and Hydrogen:

    • Ensure the number of each type of atom is the same on both sides.

  2. Balance Oxygen:

    • Add H2O\text{H}_2\text{O}H2​O to the side lacking oxygen.

  3. Balance Hydrogen:

    • Add H+\text{H}^+H+ to the side lacking hydrogen (in acidic solutions).

    • In basic solutions, neutralize H+\text{H}^+H+ by adding OH−\text{OH}^-OH− to both sides.

  4. Balance Charge:

    • Add electrons (e−e^-e−) to balance the charges in each half-reaction.

Step 3: Combine the Half-Reactions

  • Multiply each half-reaction by an appropriate factor so that the number of electrons lost in oxidation equals the number gained in reduction.

  • Add the half-reactions together, canceling out the electrons and any species that appear on both sides.

Step 4: Verify the Reaction

  • Ensure that the elements and charges are balanced in the final equation.

Balancing in Acidic and Basic Solutions

In Acidic Solutions:

  1. Use H+\text{H}^+H+ to balance hydrogen atoms.

  2. Add H2O\text{H}_2\text{O}H2​O as needed to balance oxygen.

  3. Balance the charges using electrons (e−e^-e−).

In Basic Solutions:

  1. Follow the steps for acidic solutions.

  2. Neutralize H+\text{H}^+H+ by adding OH−\text{OH}^-OH− to both sides.

  3. Simplify H++OH−→H2O\text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O}H++OH−→H2​O.

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