Oxidizing and reducing agents and spontaneity
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Oxidizing and Reducing Agents and Spontaneity. Section 13.2 Freiman. Oxidizing and Reducing Agents. A REDUCING AGENT reduces another substance by giving it electrons in a reaction Because they lose electrons, RAs are OXIDIZED

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Oxidizing and reducing agents
Oxidizing and Reducing Agents

  • A REDUCING AGENT reduces another substance by giving it electrons in a reaction

    • Because they lose electrons, RAs are OXIDIZED

  • An OXIDIZING AGENT oxidizes another substance by taking electrons from it in a reaction

    • Because they gain electrons, OAs are REDUCED


Table of redox half reactions
Table of REDOX half-reactions

  • This table is on pg. 828

  • Organized by strength of OAs an RAs

  • Strong Oxidizing Agents (SOA) are top left

  • Strong Reducing Agents (SRA) are bottom right


Spontaneity
Spontaneity

  • Not all substances will react together in a redox reaction. There is a simple rule to predict spontaneity of redox reactions:

    • If left side (SOA) HIGHER than right side (SRA), reaction is spontaneous and products will form


Examples
Examples

  • If copper(II) sulfate and zinc metal were placed in a beaker, would a spontaneous reaction occur?

  • If nickel oxide and lead metal were placed in a beaker, would a spontaneous reaction occur?


Homework
Homework

  • Read Section 13.2 – Pgs. 568-569

  • Worksheet – Oxidation and Reduction Review


Building redox tables

Building Redox Tables

Chapter 13.2

Freiman


  • The Reduction table in the data book does not contain every single OA or RA that exists.

  • Reduction tables can be made from data obtained in the lab.

  • By reacting various elements in single replacement reactions, OAs and RAs can be ranked according to strength.

    • Remembering the spontaneity rule


SOA

SRA


Example
Example

  • Using each of the following reactions, write the reduction table for tungsten, rhodium and osmium

  • Os4+(aq) + Rh(s) Os(s) + Rh3+(aq)

  • W(s) + Os4+(aq)  W6+(aq) + Os(s)

  • W(s) + Rh3+(aq)  no reaction


Steps
Steps

  • For the 1st reaction, determine the OA and the RA.

    • If reaction is spontaneous, then OA is higher than RA on the chart.

    • If NOT spontaneous, then RA is higher than OA on the chart

  • Repeat step one for all other reactions

  • Once the relative strength of all OAs and RAs have been determined, write the REDUCTION HALF REACTIONS in order of strength. (Indicate SOA and SRA in the corners)


Example 2
Example 2

  • Write a reduction half-reaction table using the information from the following lab results.

  • LaCl3(aq) + V(s) no reaction

  • LaCl3(aq) + Ga(s)  products form

  • Y(s) + VBr5(aq)  no reaction

  • GaCl3(aq) + Sc(s)  products form


Predicting redox reactions

Predicting Redox Reactions

Section 13.2

Freiman


Predicting redox reactions1
Predicting Redox Reactions

  • When performing a reaction in a solution, there may be more than one oxidizing agent or reducing agent.

  • Predicting redox reactions requires a 5-step process


Steps1
Steps

  • List all entities in solution and classify them as oxidizing or reducing agents OR BOTH

  • Choose SOA and SRA

  • Write the half-reactions

  • Balance and write the full redox reaction

  • Predict spontaneity (spontaneous or not spontaneous)


Hints
Hints

  • Aqueous solution means H2O(l) is present

  • Acidic solution means H+ is present

  • Basic solution means OH- is present

  • Some oxidizing and reducing agents are COMBINATIONS – find the combinations!

  • Watch for DISPROPORTIONATIONS – reduction and oxidation happen to the SAME ENTITY


Examples1
Examples

1. What is the redox reaction that occurs when copper metal is placed in an acidic potassium permanganate solution???

2. Can an iron container be used to transport a mixture of hydrochloric acid and zinc bromide?


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