Chemistry chapter 21


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Chemistry chapter 21

  1. 1. By Logan Danielson
  2. 2. ElectrochemistryOxidation Reduction chemistry (Electron Transfer)Remember RedOx reactions must be balanced as two separate reactions, the Oxidation half reaction and the Reduction half reaction Oxidation- involves the loss of an electron : Oil Reduction- involves the gain of an electron: Rig
  3. 3. Electrical Chemical Cells Are split up to do the half reactions separately: an anode and a cathode The anode handles the oxidation The cathode handles the reduction Electrons flow from the anode to the cathode The two half reactions are connected by the wire to allow the electrons to flow and by a salt bridge  The salt bridge prevents the build up of charge that would happen by the flow of electrons to the cathode  Cations from the salt bridge will flow into the cathode to dissipate the electron charge build up from the presence of extra electrons in the cathode  Anions from the salt bridge will flow into the anode to dissipate the electron charge build up from the absence of extra electrons in the anode
  4. 4. Galvonic cell / Voltaic CellIt does the work and produces energyCell potential – electro motive force Electrical potential is measured in Volts, V It is related in dG
  5. 5. Electrical Cell notation / Anode / Cathode Metal connected to Anode | Anode reaction || Cathode reaction | Metal connect to Cathode| = phase transition|| = salt bridge, = used to separate aqueous componentse.g.Pt(s) | Fe2+(aq)(.1M),Fe3+(aq)(.2M) || Cu2+(aq) (.1M) | Cu(s)
  6. 6. Standard Cells All solutes at 1.0 M concentration All gases at 1 atm All solids present in pure form All standard potentials are based of off an electrical cell paired with Hydrogen Eocell (in volts)= Eocathode – Eoanode  Eocell , Eocathode, and Eoanode are all written as reduction potentials  Use to predict Eocell  Used to predict spontaneously, if it was is a negative E then the reaction would happen in the opposite direction Oxidizing agents: the agent is reduced, the strongest oxidizing agents have the highest reduction potentials Reducing agents: the agent is oxidized, the strongest reducing agents have the lowest reduction potentials
  7. 7. Electrical WorkElectrical work = charge * potential difference Joules = coulombs * voltsFaraday constant, F, the magnitude of charge on one mole of electrons F= 9.65 *104 C/mol electron w=-F * potential difference wmax=-nFEcell Because wmax=dG dG=-nFEcell
  8. 8. Nerst equationEocell= .0592/n * log(K)Ecell= Eocell - .0592/n * log(Q) This allows us to predict non-standard reaction cell potentials