Lesson Notes By Weeks and Term - Senior Secondary 2

Oxidation reduction reaction

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TERM׃ 3RD TERM

WEEK THREE

Class: Senior Secondary School 2

Age: 16 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic:- Oxidation reduction reaction.

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Define oxidation reaction
  2. define reduction reaction.
  3. Define Redox reaction
  4. Identify oxidation number of some central elements .

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher explains how oxidation and reduction work together.

Students pay

attention

STEP 2

EXPLANATION

He defines Redox reaction and also identify oxidation number of some central elements.

Students pay

attention and

participate

STEP 3

NOTE TAKING

The teacher writes a summarized

note on the board

The students

copy the note in

their books

 

NOTE

OXIDATION REDUCTION (REDOX) REACTIONS

Reduction reaction

A reduction reaction is a chemical process where a substance gains electrons, leading to a decrease in its oxidation state. This type of reaction often involves the addition of electrons, hydrogen, or the removal of oxygen. Reduction reactions commonly occur alongside oxidation reactions in redox reactions.

Redox reaction

A redox (reduction-oxidation) reaction is a chemical process in which one substance undergoes oxidation (loses electrons) while another substance undergoes reduction (gains electrons). This simultaneous exchange of electrons between reactants leads to changes in oxidation states. Redox reactions are fundamental in various natural and industrial processes, including combustion, corrosion, photosynthesis, and cellular respiration. The substance donating electrons is the reducing agent, and the one accepting electrons is the oxidizing agent. The overall process ensures conservation of charge and often involves a transfer of energy.

Oxidation number

An oxidation number is a number that is assigned to an atom in a substance. The oxidation number could be positive, negative, or zero, and it indicates if electrons are lost or gained. In other words, the oxidation number is a number that helps us keep track of electrons in an atom.

Here, the oxidation number of calcium is +2 and the oxidation number of oxygen is -2.

If the oxidation number is positive, then this means that the atom loses electrons, and if it is negative, it means the atom gains electrons. If it is zero, then the atom neither gains nor loses electrons.

Calcium has a +2 charge, which means it lost two electrons. Oxygen has a -2 charge, which means it gained two electrons.

Key points about oxidation numbers:

  1. General Guidelines:

   - For elements in their elemental form (e.g., O₂, H₂), the oxidation number is 0.

   - For monatomic ions, the oxidation number is equal to the charge of the ion (e.g., Na⁺ has an oxidation number of +1).

  1. Variable Oxidation States:

   - Transition metals often exhibit variable oxidation states. For example, iron can be +2 or +3.

   - Nonmetals in groups such as nitrogen and sulfur can have multiple oxidation states.

  1. Sum of Oxidation Numbers:

   - In a neutral compound, the sum of oxidation numbers is zero.

   - In ions, the sum of oxidation numbers is equal to the charge of the ion.

  1. Binary Ionic Compounds

The oxidation number of each element in a binary ionic compound is equal to the charge on that element. The charge can be found by looking at the periodic table, and are based on the group that the element is found in:

Group 1 elements: +1 charge

Group 2 elements: +2 charge

Group 13 elements: +3 charge

Group 14 elements: +4 charge

Group 15 elements: -3 charge

Group 16 elements: -2 charge

Group 17 (halogen) elements: -1 charge

Group 18 (noble gases) elements: 0 charge (these do not typically react)

The oxidation number of the following ionic compounds can be determined based on the charges:

NaCl : sodium is in group 1 with an oxidation number of +1, and chlorine is in group 17 with an oxidation number of -1

Ca2 : calcium is in group 2, with an oxidation number of +2, iodine is in group 17, with an oxidation number of -1, but there are two of them, so there is an oxidation number of -2

Ca3P2 : calcium is in group 2, with an oxidation number of +2, there are 3 of them, so the total oxidation number is +6. Phosphorous is in group 16, with an oxidation number of +3, there are 2 of them so the total oxidation number is -6

FeCl3 : chlorine is in group 17, with an oxidation charge of -1, there are three of them, so the total oxidation number is -3. Iron is a transition metal, and the charge can vary, in this case, it can be determined because the total charge of the compound needs to be 0 since the oxidation number on the chlorine is -3, the oxidation number on the iron needs to be +3.

EVALUATION:   1. Define Redox reaction.

  1. Differentiate between oxidation reaction and reduction reaction and show how they relate with each other.
  2. What is oxidation number.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively