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Sarah Taylor

HS-PS1-2

Balancing Redox Reactions Study Guide

Balancing redox reactions includes oxidation and reduction processes that take place simultaneously.

Introduction

  • Redox reaction or oxidation-reduction reaction includes the transfer of particles during a chemical reaction.
  • Balancing redox reaction includes several methods, such as half-reaction, where one is done through oxidation, and another half represents the reduction. And then, the half-reactions are added together, resulting in the entire balanced equation.

WHAT IS REDOX REACTION BALANCING?

Redox equations are said to be more complex than the standard reaction. This balancing includes a half-reaction table and is often split up into two parts to get one net balanced equation.

  • The loss of electrons due to the transfer of electrons in the given reactant and the increase of the reactant in the oxidation state is called oxidation.
  • In contrast, the gain of electrons and the decrease of reactants in the oxidation state is said to be the reduction process.
  • The accepting electrons always undergoes a reduction in redox reactions and are thus called oxidizing agents.
  • The donor of the electron undergoing an oxidation process in a redox reaction is called a reducing agent.

HOW TO BALANCE A REDOX REACTION (HALF-REACTION METHOD)?

  • We divide the equation into two half in this procedure.
  • After that, we split the two portions of the reaction and balance them independently.
  • Finally, we combine them to get a balanced equation.

We'll use an example to show the procedures involved in balancing redox reactions using the half-reaction approach.

In an acidic solution, for example, Fe2+ ions are transformed into Fe3+ ions by dichromate ions. In the process, dichromate ions (Cr2O72–) are reduced to Cr3+ ions. The redox process described above must be balanced. The following are the steps to balancing this equation.

Step 1: First, we must express the equation in its simple ionic form.

Fe2+9aq) + Cr2O72-(aq) -> Fe3+9aq) + Cr3+(aq)

Step 2: Split the equation into two halves, one for oxidation and one for reduction.

Fe2+(aq) -> Fe3+9aq) Oxidation Half

Cr2O72-(aq) -> Cr3+(aq) Reduction Half

Step 3: We shall balance the atoms present in each half of the reaction excluding O and H atoms in the third phase of balancing redox reactions using the half-reaction method.

  • The oxidation phase of the reaction in terms of Fe atoms is already balanced in the example question.
  • As a result, we'll only balance the reaction's reduction phase.
  • To balance the Chromium atoms in this example, we shall multiply Cr3+ by 2.

Cr2O72-(aq) -> 2Cr3+(aq)

Step 4: We know that the reaction occurs in an acidic environment. As a result, we must add water molecules (H2O) to balance the O atoms in the equation, as well as H+ to balance the H atoms.

The equation is now: Cr2O72-(aq) + 14H+(aq) -> 2Cr3+(aq) + 7H2O (1)

Step 5: Now we must balance the charges in both halves of the reaction.

  • As a result, we must multiply the appropriate number by one or both halves of the reaction to equalize the number of electrons.
  • The oxidation portion of the reaction must be balanced.

Fe2+(aq) -> Fe3+(aq) + e-

  • There are 12 positive charges on the left side of the equation for the reduction half and 6 positive charges on the right side of the equation for the reduction half.
  • To balance the reduction half, we must add 6 extra electrons to the left side of the equation.

Cr2O72-(aq) + 14H+(aq) + 6e -> 2cr3+(aq) + 7H2O (1)_

  • We'll double 6 in the oxidation half-reaction to equalize the electrons in the two parts of the reaction. As a result,

Step 6: To complete the total reactions, the two halves of the equations are joined together.

  • Cancel the electrons on both sides after adding the two reaction halves. The net ionic equation is as follows:

6Fe2+(aq) + Cr2O72-(aq) + 14H+(aq) -> 6Fe3+(aq) + 2Cr3+(aq) + 7H2O(1)

Step 7: Finally, we must ensure that both sides of the equation have the same type, quantity, and charges. Furthermore, in terms of atoms and charges, the equation is perfectly balanced.

In the case of a basic solution, we must balance the atoms in the same way that we would in an acidic solution. Then, in both half of the equation, an equal number of OH– ions are added for each H+ ion. When H+ and OH– ions are present on the same side of the equation, the ions must be combined to form H2O.

SUMMARY

  • Any chemical reaction in which oxidation and reduction both processes take place simultaneously is know as a redox reaction.
  • The half-reaction method is a way to balance redox reactions. It involves breaking the overall equation down into an oxidation part and a reduction part.

FAQ’s

1. What are 2 ways of balancing redox reactions?

Two ways are:

  • Oxidation number method
  • Half reaction method

2. How do you balance redox reactions Class 11?

  • To balance the redox reaction, first check the nature of the reaction.
  • If the reaction is of acidic nature, balance the charges by adding H ions.
  • For basic nature, add OH- ions.
  • Then, balance the deficient side of oxygen atoms by adding the required molecules. This way, you get balanced redox equations.

3. What is Ncert Class 10 redox?

A redox reaction is a reaction in which one reactant undergoes a reduction process, and the other gets oxidized during the reaction. It is termed a reduction-oxidation reaction.

4. How do you balance redox reactions fast?

  • Divide the equation into two halves
  • Balance each half-equation for mass and charge
  • Equalize the electron numbers and then mix both the equations.

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Sources

  1. Balancing Redox Reaction: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Redox_Chemistry/Balancing_Redox_reactions.Accessed 28 Feb 2022.
  2. Balancing Redox Reaction: https://courses.lumenlearning.com/introchem/chapter/balancing-redox-equations-2/. Accessed 28 Feb 2022.
  3. Redox Reactions: https://byjus.com/jee/redox-reactions/. Accessed 28 Feb 2022.
  4. Balancing Redox Reaction: https://opentextbc.ca/introductorychemistry/chapter/balancing-redox-reactions/. Accessed 28 Feb 2022.