redox reactions reactants: zn + i 2 product: zn i 2

Redox ReactionsRedox Reactions


Reactants: Zn + IReactants: Zn + I22 Product: Zn IProduct: Zn I22

Redox Equations:Redox Equations:At the conclusion of our time together, At the conclusion of our time together,

you should be able to:you should be able to:

1.1. Define redoxDefine redox2.2. Figure out oxidation numbers for any Figure out oxidation numbers for any

elementelement3.3. Show the change in oxidation numbers in a Show the change in oxidation numbers in a

reactionreaction

Little Known Phobias!Little Known Phobias!

VacatianoiaVacatianoia

mental state created en route to one's vacation, when someone asks whether

anyone remembered to turn off the iron!

What’s the Point ?What’s the Point ?

• Electrical production (batteries, fuel cells)

REDOX reactions are important in …

• Purifying metals (e.g. Al, Na, Li)

• Producing gases (e.g. Cl2, O2, H2)

• Electroplating metals

• Protecting metals from corrosion• Balancing complex chemical equations

• Sensors and machines (e.g. pH meter)

C3H8O + CrO3 + H2SO4 Cr2(SO4)3 + C3H6O + H2O

What is Redox?What is Redox?

REDOX stands for REDuction/OXidation Oxidation is often thought of as a combination of

a substance with oxygen (rusting, burning) Oxidation refers to a loss of electrons Reduction refers to a gain of electrons As a mnemonic remember LEO says GER

• Loss Electrons = Oxidation• Gain Electrons = Reduction

To: Santa Re: Where Are My Gifts?!To: Santa Re: Where Are My Gifts?!

Actual E-mails to EmailSanta.comActual E-mails to EmailSanta.com

Pleease! Don’t bring me any new clothes.Pleease! Don’t bring me any new clothes.

Kayla, 9Kayla, 9

Let’s See How You’re Doing??Let’s See How You’re Doing??

Q- What is oxidation? What is reduction? Q- What is oxidation? What is reduction? Represent each as a chemical equation.Represent each as a chemical equation.

oxidation oxidation = loss of e= loss of e–– … … X X X X+ + + e+ e– –

reduction reduction = gain of e= gain of e–– … … X + eX + e– – X X––

Q- Why is 2Na + ClQ- Why is 2Na + Cl22 2NaCl considered a redox 2NaCl considered a redox reactions?reactions?

This involves the transfer of electrons. (Na has no This involves the transfer of electrons. (Na has no charge, the atoms in diatomic molecules have no charge, the atoms in diatomic molecules have no partial charge. After reaction the atoms have partial charge. After reaction the atoms have different shares of the electrons because of different shares of the electrons because of different EN values)different EN values)


Q- Is it possible to oxidize a material without reducing Q- Is it possible to oxidize a material without reducing something else?something else?

No. A lost eNo. A lost e–– is taken up by something else. is taken up by something else.

My new book on GOLF will give My new book on GOLF will give the reader valuable playing tips the reader valuable playing tips

and insider information I've and insider information I've gained through my years of gained through my years of

lessons, struggles and lessons, struggles and experiments.experiments.

Here are just a few of the Here are just a few of the chapter titles: chapter titles:

Chapter 19 - Throwing Your Clubs: An Chapter 19 - Throwing Your Clubs: An Effective Stress-Reduction Technique.Effective Stress-Reduction Technique.Chapter 15 - How to Relax When You Chapter 15 - How to Relax When You

Are Hitting Five Off the Tee.Are Hitting Five Off the Tee.

Determination of Oxidizing and Reducing Determination of Oxidizing and Reducing AgentsAgents

I.I. Determine oxidation # for all Determine oxidation # for all atoms in both the reactants atoms in both the reactants and products.and products.

II.II. Look at the same atom in Look at the same atom in reactants and products and reactants and products and see if oxidation # increased see if oxidation # increased or decreased.or decreased. If oxidation # decreased; If oxidation # decreased;

substance reducedsubstance reduced If oxidation # increased; If oxidation # increased;

substance oxidized substance oxidized

Determination of Oxidizing and Reducing Determination of Oxidizing and Reducing Agents (continued)Agents (continued)

Oxidizing AgentOxidizing Agent: Substance that : Substance that oxidizes the other substance by oxidizes the other substance by accepting electrons. It is accepting electrons. It is reduced in reaction.reduced in reaction.

Reducing AgentReducing Agent: Substance that : Substance that reduces the other substance by reduces the other substance by donating electrons. It is oxidized donating electrons. It is oxidized in reaction.in reaction.


Q-Q- Define oxidizing agent, reducing Define oxidizing agent, reducing agent.agent.

An oxidizing agent causes oxidation An oxidizing agent causes oxidation by being reduced itselfby being reduced itself

A reducing agent causes reduction by A reducing agent causes reduction by being oxidized itselfbeing oxidized itself

Review of Oxidation NumbersReview of Oxidation Numbers

We will see that there is a simple way to keep track We will see that there is a simple way to keep track of oxidation and reductionof oxidation and reduction

This is done via “oxidation numbers”This is done via “oxidation numbers” An oxidation number is the charge an atom would An oxidation number is the charge an atom would

have if electrons in its bonds belonged completely to have if electrons in its bonds belonged completely to the more electronegative atomthe more electronegative atom

e.g. in HCl, Cl has a higher EN. Thus, oxidation e.g. in HCl, Cl has a higher EN. Thus, oxidation numbers are Cl = -1, H = +1numbers are Cl = -1, H = +1

Notice that oxidation numbers are written as +1 vs. Notice that oxidation numbers are written as +1 vs. 1+ to distinguish them from charges.1+ to distinguish them from charges.

1.1. Any element, when not combined with atoms of a Any element, when not combined with atoms of a different element, has an oxidation # of zero. different element, has an oxidation # of zero. (O in O(O in O22 is zero, Na by itself is zero) is zero, Na by itself is zero)

2.2. Any simple monatomic ion (one-atom ion) has an Any simple monatomic ion (one-atom ion) has an oxidation number equal to its charge oxidation number equal to its charge (Na(Na++ is +1, O is +1, O2–2– is –2) is –2)

3.3. The sum of the oxidation numbers of all of the The sum of the oxidation numbers of all of the atoms in a formula must equal the charge written atoms in a formula must equal the charge written for the formula. (if the oxidation number of O is –2, for the formula. (if the oxidation number of O is –2, then in COthen in CO22 the oxidation number of C is +4) the oxidation number of C is +4)

Oxidation Numbers RulesOxidation Numbers Rules

4.4. In compounds, the oxidation # of IA metals is +1, In compounds, the oxidation # of IA metals is +1, IIA is +2, IIIA is +3, 13 is +3, Zn & Cd is +2, IIA is +2, IIIA is +3, 13 is +3, Zn & Cd is +2, Ag is +1.Ag is +1.

5.5. In ionic compounds, the oxidation # of a In ionic compounds, the oxidation # of a nonmetal or polyatomic ion is equal to the charge nonmetal or polyatomic ion is equal to the charge of its associated ion. of its associated ion. (MgCl(MgCl22, , Mg is +2, therefore Cl is –1)Mg is +2, therefore Cl is –1)

6.6. F is always –1, O is always –2 F is always –1, O is always –2 (unless combined with F), (unless combined with F),

H is usually +1, H is usually +1, exceptexcept when it is when it is bonded to metals in binary bonded to metals in binary

compounds. compounds. (ex. NaH, H oxidation # is (ex. NaH, H oxidation # is ––1 1 oror when it’s in when it’s in elemental form elemental form HH22, oxidation # is 0)., oxidation # is 0).

Oxidation Number RulesOxidation Number Rules

NaIO3

Na = +1O = -2

3x(-2) + 1 + ? = 0 I = +5

IF7

F = -1

7x(-1) + ? = 0

I = +7

Oxidation numbers of all the elements in the following ?

What Kind Of Coffee Was What Kind Of Coffee Was Served On The Titanic?Served On The Titanic?

Sanka.Sanka.

Redox Equations:Redox Equations:Let’s see if you can:Let’s see if you can:

1.1. Define redoxDefine redox2.2. Figure out oxidation numbers for any Figure out oxidation numbers for any

elementelement3.3. Show the change in oxidation numbers in a Show the change in oxidation numbers in a

reactionreaction

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Yesterdays Meals on Wheels

RuleRuleTotalTotalOx.#Ox.# +1

6+1

-2

6-6+5

3

+5 +1

4+2

-2

6-14+12

3

+6

or rule 5

+1

6+6

-2

6-2-4

3

-2 -1

5-1+1

4

+1H N O 3 C2H6OK2Cr2O7

AgI+1

6+2

-2

6-8+5

3

+5H2PO4

–

Let’s Apply the Oxidation RulesLet’s Apply the Oxidation Rules

Familiar SayingFamiliar Saying

Glucose reveries.

Sugar high!!

Corrosion – Deterioration of Metals by Corrosion – Deterioration of Metals by Electrochemical ProcessElectrochemical Process

Let’s consider what happened to the iron ribbing of the Statue of Liberty

Iron loses e-, therefore is oxidizedOxygen gaines e-, therefore is reduced

Iron loses e-, therefore is the reducing agent

Oxygen gaines e-, therefore is the oxidizing agent

Corrosion – Deterioration of Metals by Corrosion – Deterioration of Metals by Electrochemical ProcessElectrochemical Process

Determine and balance the reaction, determine what is oxidized and what is reduced.

Corrosion of SilverCorrosion of Silver

Ag + O2 Ag2O

4 Ag + O2 2 Ag2O

Each Ag loses 1e--

Each O gains 2e--

Silver = oxidizedOxygen = reducedSilver = reducing agentOxygen = oxidizing agent

Hey, We’re Done, That’s Something to Cheer About!!!

Things my Mother taught me…

IRONY.

"Keep crying, and I'll give you something to cry about."

Redox Equations:Redox Equations:At the conclusion of our time together, At the conclusion of our time together,

you should be able to:you should be able to:

1.1. Review redoxReview redox2.2. Review oxidation numbers for any elementReview oxidation numbers for any element3.3. Show the change in oxidation numbers in a Show the change in oxidation numbers in a

reaction and show the reactionreaction and show the reaction

What is Redox?What is Redox?

REDOX stands for REDuction/OXidation Oxidation is often thought of as a combination of

a substance with oxygen (rusting, burning) Oxidation refers to a loss of electrons Reduction refers to a gain of electrons As a mnemonic remember LEO says GER

• Loss Electrons = Oxidation• Gain Electrons = Reduction


Q- What is oxidation? What is reduction? Q- What is oxidation? What is reduction? Represent each as a chemical equation.Represent each as a chemical equation.oxidation oxidation = loss of e= loss of e–– … … X X X X+ + + e+ e– –

reduction reduction = gain of e= gain of e–– … … X + eX + e– – X X––

Q- Why is 2Na + ClQ- Why is 2Na + Cl22 2NaCl considered a redox 2NaCl considered a redox reactions?reactions?

This involves the transfer of electrons. This involves the transfer of electrons. The oxidation numbers change for 2 elements.The oxidation numbers change for 2 elements.Na goes from 0 to Na goes from 0 to

+1+1Cl goes from 0 to Cl goes from 0 to

-1-1

Interesting Answers to Catholic Elementary School Bible Questions:

Solomon, one of David’s sons, had 300 wives and 700 porcupines.


Q- Is it possible to oxidize a material without reducing Q- Is it possible to oxidize a material without reducing something else?something else?

No. A lost eNo. A lost e–– is taken up by something else. is taken up by something else.



Each Zn loses 2e--

Each I gains 1e--

Zinc = oxidizedIodine = reducedZinc = reducing agentIodine = oxidizing agent

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These are statements people actually said in court, word for word, taken down and now published by court

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redox reactions reactants: zn + i 2 product: zn i 2

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