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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 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 • 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 • 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 • 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 • 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 • Read Section 13.2 – Pgs. 568-569 • Worksheet – Oxidation and Reduction Review
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 • 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 • 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 • 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 Section 13.2 Freiman
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
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 • 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
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?