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Redox IntroWhat we knowOxidation states are the charges of ions Ions have gained or lost electronsLoosing electrons will make it a positive chargeGaining electrons will make it a negative chargeA neutral compound has equal numbers of positive and negative ions Matter and particles cant just disappearLaw of conservation of massCompoundsNaClNeutral Compound: no charge1+1-In order for a compound to be neutral, it must have equal numbers of positive and negative chargesDetermining Oxidation StateSome elements only have one oxidation state possible when they form an ion: Na1+Be2+B3+Other elements have multiple possibilities: Cl1+, Cl3+, Cl5+, Cl7+, Cl1-Determining Oxidation StateUse elements that cant change to figure out the charge on elements that have choices. Br2O52-10-10+5+What is the oxidation state of Iron (Fe) in FeF2?1+2+3+4+What is the oxidation state of nitrogen (N) in N2S3?+1+2+3+4+5Oxidation StatesOn its own, an element has an oxidation state of 0Protons equals the number of electrons

Na + HCl H2 + NaCl001+1+1-1-Fe2O3 FeO + O2Redox ReactionsIn the process of a chemical reaction, the oxidation state of an element can change. Fe2O3 FeO + O23+2+2-2-03+2+e1- +

Half ReactionsGain Electron: Reduction e1- + Fe3+ Fe2+Lose Electron: OxidationN2+ N3+ + e1-

LEO says GERLEO says GERIf the oxidation state becomes more positive, the ion has lost electrons (oxidized)If the oxidation state becomes more negative, the ion has gained electrons (reduced)Li Li01++ e1-Lose Electron OxidationIs the following half reaction showing reduction or oxidation? Fe2+ Fe3+ + e1-Oxidation ReductionIs the following half reaction showing reduction or oxidation? Fe0 Fe2+ + 2e1-Oxidation ReductionIs the following half reaction showing reduction or oxidation? e1- + N1- N2-Oxidation ReductionWhich of the following elements will undergo reduction? SodiumBariumAluminumNitrogenWhich of the following elements will undergo oxidation to form an ion? PotassiumPhosphorusBromineArgonWriting Half ReactionsHalf reactions show the gain or loss of electrons in a chemical reaction. They only show one element either gaining or losing electrons2H2 + O2 2H2O2H2 + O2 2H2O4e-1 +0-2Writing Half Reations2KCl 2K + Cl2Writing Half ReactionsZn + 2HCl H2 + ZnCl2Redox Reactions:Voltaic CellsWhat we knowAtoms can gain or lose electrons to form ionsLEO says GER: Lose Electron oxidation Gain Electron ReductionElectrons are transferred between ionsVoltaic CellVoltaic Cells harness the transfer of electrons in redox reactions to help power electronic devises

e-e-Voltaic CellsBy separating the two ions in a reaction, we can force the electrons to pass through a wire and to do work for us. Zne-Cue-Voltaic Cell

Voltaic Cell

Red CatAn OxReduction happens at the cathodeOxidation happens at the anodeSalt Bridge

In order to keep the system electrically balanced, you have to have a way to balance the charges

The salt bridge allows ions to travel between half-cells. Voltaic Cell

Electrons travel from the anode to the cathode. Anode and CathodeAnode: where oxidation happensCathode: where reduction happensThe most reactive metal will undergo oxidation and lose its electrons

Electrolytic CellIf a battery is put into the loop, it can drive the system backwards.

Electrons flow towards the anode and reduction occurs at the anode. If copper and gold are used as electrodes, copper will be the CathodeAnodeSalt BridgeSolutionThe purpose of a salt bridge is toAllow the passage of electronsAllow the passage of waterAllow the passage of ionsPrevent the passage of electricityA voltaic cell differs from a electrolytic cell in that itDoes not involve oxidationDoes not use a batteryDoes not use a salt bridgeDoes not generate electricityOxidation occurs at the CathodeSalt BridgeSolutionAnodeWhich of the following ions undergoes reduction? Li Li1+Cu2+ Cu1+Mg1+ Mg2+Zn Zn2+What is Electricity?What we knowElectrons are negatively charged particles whose configuration determines the chemical properties of elementsWhen an atom gains an electron it becomes negatively charged. When an atom loses an electron, it becomes positively charged. In REDOX reactions, electrons from one element are transferred to another elementElectricityElectricity is the movement of electronsWe power machines and electronics by harnessing the power of moving electronsMoving electrons generate a magnetic field by which we can spin an axle.

Design ChallengeIf we wanted to design an electric car, we would have to develop a way to generate electrons for a motor. What are the basics to batteries?

What do we know about batteries? Batteries: Redox ReactionsWe know that redox reactions involve the transfer of electrons between elementsFeSFe2+S2- Two electrons are transferred between iron and sulfur. This does not produce usable electricity as it is instantaneous. Batteries: Redox ReactionsWe need to separate the two elements so that the electrons transferred can be diverted temporarily. Se1-e1-FeFe2+S2-Batteries: Voltaic CellsElectrons flow from the negative electrode to the positive electrode. On one end of the battery are elements that want to gain electrons and on the other are elements that want to lose electrons. e-1

Batteries: Voltaic CellsIn every battery there are at least two cells of chemicals.

Batteries: Voltaic CellsThe elements that lose electrons undergo oxidationThe elements that gain electrons undergo reduction

OxidationReductionParts of a Voltaic Cell

ElectrodeElectrodeSalt BridgeWireWireSalt SolutionSalt SolutionCu2+Parts of a Voltaic CellElectrodes: The place where electrons are gained or lost (reduction or oxidation)

e1-e1-A copper ion gains two electrons and becomes solid copper metal. Parts of a Voltaic CellSalt Bridge: Allows for the two salt solutions to stay electrically balanced (neutral), Allows IONS to flow throughNa+Na+Na+Na+Na+Na+Na+Na+Parts of a Voltaic CellWire: Allows the electrons to flow from the ANODE to the CATHODE, flow from the negative to the positive electrodese1-e1-e1-e1-Parts of a Voltaic CellSalt Solution: Provides ions for the reduction and oxidation process, provides ions for maintaining electrical neutrality of the cellsCuCu2+Cu2+Cu2+Cu2+Cu2+A copper electrode typically sits in a solution of copper ions. Predicting Electron FlowHow do we figure out if an electrode will gain or lose electrons? The more reactive element will lose electrons (be oxidized) based on Table J.

An OxOxidation occurs at the ANODEPredicting Electron FlowFeMge-1Predicting Electron FlowCsNie-1Predicting Electron FlowZnAue-1Predicting Electron FlowKLie-1