Assalamu’alaikum…^_^

Welcome to Chemistry LearningThe …th meeting of the class !!!

“Oxidation-Reduction Reactions”

(Equalization Method of Equation Redox Reaction)

Created by:Nadya Raudotul Jannah0905699

In X grade, you have ever studied about redox

reaction.

Do you still remember, what is the meaning of oxidation and reduction

reaction?!?

Aperseption :

What do you know about oxidation number?!?

And how to determine the oxidation number of the element?!?

Remember…^_^

LEO SAYS GER

LEO says GER : Lose Electrons = Oxidation

eNaNa10

Sodium is oxidized

Gain Electrons = Reduction

10 CleCl Chlorine is reduced

LEO says GER : - Losing electrons is oxidation, and the substance

that loses the electrons is called the reducing agent.

- Gaining electrons is reduction, and the substance that gains the electrons is called the oxidizing agent.

Mg is oxidized: loses e-, becomes a Mg2+ ion

Mg(s) + S(s) → MgS(s)

Mg is the reducing

agent

S is the oxidizing agent S is reduced: gains e- = S2- ion

Oxidation and Reduction (Redox)It is easy to see the loss and gain of electrons in ionic compounds, but what about covalent compounds?

In water, we learned that oxygen is highly electronegative, so:

the oxygen gains electrons (is reduced and is the oxidizing agent), and the hydrogen loses electrons (is oxidized and is the reducing agent)

Exploration :

Does each chemical reaction must be equal?!?

What do you know about equalization of chemical reaction?!?Does the simple

chemical reaction can be equal with spontan method?!?

The Meaning of Oxidation and Reduction (called “redox”) Learning Objectives

After Learning this topic, you are expected to be able to:

Describe how oxidation numbers are used to identify redox reactions.

Balance a redox equation using the oxidation-number-change method.

Balance a redox equation by breaking the equation into oxidation and reduction half-reactions, and then using the half-reaction method.

Concept MapRedox Reaction and Electrochemistry

Electrochemical Cell

Alectrolysis Cell

Redox Reaction

Reaction Equalizati

on

Cell Potential

Standard Reduction Potential

Half Reaction

Oxidation Number

based onincluding

Is cunducted

by means of

In general, all chemical reactions can be assigned to one of two classes:

1) oxidation-reduction, in which electrons are transferred:

• Single-replacement, combination, decomposition, and combustion

2) this second class has no electron transfer, and includes all others:

• Double-replacement and acid-base reactions

Identifying Redox Equations

Identifying Redox Equations

In an electrical storm, nitrogen and oxygen react to form nitrogen monoxide:

N2(g) + O2(g) → 2NO(g)

• Is this a redox reaction?• If the oxidation number of an element

in a reacting species changes, then that element has undergone either oxidation or reduction; therefore, the reaction as a whole must be a redox.

YES!

Balancing Redox Equations

It is essential to write a correctly balanced equation that represents what happens in a chemical reaction• Fortunately, two systematic methods

are available, and are based on the fact that the total electrons gained in reduction equals the total lost in oxidation. The two methods:

1) Use oxidation-number changes

2) Use half-reactions

Using Oxidation-Number Changes

Sort of like chemical bookkeeping, you compare the increases and decreases in oxidation numbers.• start with the skeleton equation• Step 1: assign oxidation numbers to all atoms;

write above their symbols• Step 2: identify which are oxidized/reduced• Step 3: use bracket lines to connect them• Step 4: use coefficients to equalize• Step 5: make sure they are balanced for both

atoms and charge

For Example:

Please Look at the Video

Elaboration :

What All Reactions that occur in the world are Redox Reactions?!?

What method that can be used to equal reaction but not redox reaction?!?

Not All Reactions are Redox Reactions

- Reactions in which there has been no change in oxidation number are NOT redox reactions.

Examples:

)()()()( 3

2511111

3

251

aqONNasClAgaqClNaaqONAg

)()()()(22

2

1

4

26

2

1

4

26

2

1121

lOHaqOSNaaqOSHaqHONa

Using half-reactions A half-reaction is an equation showing just the oxidation or just the reduction that takes place

they are then balanced separately, and finally combined

Step 1: write unbalanced equation in ionic form

Step 2: write separate half-reaction equations for oxidation and reduction

Step 3: balance the atoms in the half-reactions

(More steps on the next slide)

Using half-reactions (Cont’)• Step 4: add enough electrons to one

side of each half-reaction to balance the charges

• Step 5: multiply each half-reaction by a number to make the electrons equal in both

• Step 6: add the balanced half-reactions to show an overall equation

• Step 7: add the spectator ions and balance the equation

For Example:

Please Look at the Video

Any Question ?!?

who can explain the main topic

about this matter?!?

Choosing a Balancing Method

1) The oxidation number change method works well if the oxidized and reduced species appear only once on each side of the equation, and there are no acids or bases.

2) The half-reaction method works best for reactions taking place in acidic or alkaline solution.

Comfirmation:

Conclution Reactions in which there has been change in oxidation

number are called redox reactions. Every redox reactions consists of half reaction (oxidation

reaction) and half reaction (reduction reaction). Oxidation is various types of process that naturally to

increase valence from vital element in that system. Initial oxidation is in the form of reaction from elements with oxygen, then with halogen too, and ultimately its vital elements reaction loses its valence electron.

Reduction is hydrogen addition of intake in any substance, oxidation degree depression of any elements in compound, or electron addition in any elements atom.

Redox reaction quotation must be equal between left and right field. The applied method for equalizing redox reaction is oxidation number and half reaction method.

Evaluation:

Exchange and equalize the following redox reaction equation:

a. Zn(s) + SO42-(aq) Zn2+(aq) + SO2(g)

b. Fe2+(aq) + MnO4-(aq) Fe3+(aq) +

MnO2(s)

c. CN-(aq) +MnO4-(aq)+H2O(l) MnO2(s)

+ CNO-(aq) + OH-(aq)

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SER Thanks for Your Attention !!!

Wassalamu’alaikum…^_^