Chapter 20 Electrochemistry：20章电化学完整版.pptxVIP

Chemistry,TheCentralScience,10thedition

TheodoreL.Brown;H.EugeneLeMay,Jr.;andBruceE.Bursten

Chapter20

Electrochemistry

JohnD.Bookstaver

St.CharlesCommunityCollege

St.Peters,MO

2006,PrenticeHall,Inc.

•REDOXREACTIONS–

•HOWTOASSIGNOXIDATIONNUMBERS

•HOWTOBALANCEREACTIONSINACIDANDBASICMEDIUMUSINGTHEHALFREACTIONMETHOD

•HW:13,15,17,19

APRIL8

ElectrochemicalReactions

Inelectrochemicalreactions,electronsaretransferredfromonespeciesto

another.

Metalstendtoloseelectronsandareoxidized,nonmetalstendtogain

electronsandarereduced.

Gaining

ElectronsisReduction

Losing

ElectronsisOxidation.

LEOGER

•Oxidation•Is

•Loss.

•Reduction•Is

Gain.

OILRIG

•Arereduction–

oxidationreactions.

•Electronsaretransferred.

•Whenanatomis

losingelectronsitsO.N.increases.Itisbeingoxidized.

•Whenanatomgains

electronsitsO.N.

decreases.Itisbeing

REDOXREACTIONS

reduced

Inordertokeep

trackofwhatloseselectronsandwhatgainsthem,we

assignoxidationnumbers.

OxidationNumbers

AssigningOxidationNumbers

1.ElementsintheirelementalformhaveanON=0.

2.Theoxidationnumberofamonatomicionisitscharge.

3.Nonmetalstendtohavenegativeoxidation

numbers,althoughsomearepositiveincertaincompoundsorions.

➢Oxygenhasanoxidationnumberof-2,

exceptintheperoxideioninwhichithasanoxidationnumberof-1.

➢Hydrogenis+1exceptinmetalhydrideswhenis-1.

➢Fluorinealwayshasanoxidationnumberof-1.

Electrochemistry

8

AssigningOxidationNumbers

➢Theotherhalogenshaveanoxidation

numberof-1whentheyarenegative;

theycanhavepositiveoxidationnumbers,however,mostnotablyinoxyanions

4.Thesumoftheoxidationnumbersina

polyatomicionisthechargeontheion.

4.Thesumoftheoxidationnumbersinaneutralcompoundis0.

•Aspeciesisoxidized