electrochemistry cuso 4 (aq) zn znso 4 (aq) zn cu
TRANSCRIPT
ElectrochemistryElectrochemistry
CuSO4(aq)
Zn
ZnSO4(aq)
Zn
Cu
ElectrochemistryElectrochemistry
BatteryBattery – uses the energy from a – uses the energy from a redox reaction to produce an redox reaction to produce an electric current and do work.electric current and do work.
ElectrochemistryElectrochemistry – the study of – the study of the interchange of chemical and the interchange of chemical and electrical energy.electrical energy.
ElectrochemistryElectrochemistry
2 Types of electrochemical processes2 Types of electrochemical processes1.1. The production of an electric The production of an electric
current from a chemical (redox) current from a chemical (redox) reaction – battery, voltaic cell, reaction – battery, voltaic cell, galvanic cell.galvanic cell.
2.2. The use of an electrical current to The use of an electrical current to produce a chemical change (redox produce a chemical change (redox reaction). Call this electrolysis.reaction). Call this electrolysis.
ElectrochemistryElectrochemistry
How do we capture the energy?How do we capture the energy? Separate the oxidizing agent Separate the oxidizing agent
(electron acceptor) from the (electron acceptor) from the reducing agent (electron donor)reducing agent (electron donor)
Requires the electron transfer to Requires the electron transfer to occur through a wire or an occur through a wire or an electric motor! electric motor!
Figure 18.1: Schematic for separating the Figure 18.1: Schematic for separating the oxidizing and reducing agents in a redox oxidizing and reducing agents in a redox reaction.reaction.
8H+ + MnO4- + 5e- Mn2+ + 4H20 ; Fe2+ Fe3+ + e-
Why is thereno flow ofelectrons here?
Figure 18.2: Electron Figure 18.2: Electron flow.flow.
8H+ + MnO4- + 5e- Mn2+ + 4H20 ; Fe2+ Fe3+ + e-
Build up of chargeswould require largeamounts of energy
Solutions mustbe connectedto allow ionsto flow
Figure 18.4: The salt Figure 18.4: The salt bridge contains a strong bridge contains a strong electrolyte.electrolyte.
Figure 18.4: The porous disk allows ion flow.
ElectrochemistryElectrochemistry
Want to allow ions to flow but not Want to allow ions to flow but not mix the solutionsmix the solutions
Electrons flow in the wire from Electrons flow in the wire from reducing agent to oxidizing agentreducing agent to oxidizing agent
Electrochemical Electrochemical battery (galvanic cell) battery (galvanic cell) A device powered by a redox A device powered by a redox
reactions where the oxidizing reactions where the oxidizing agent is separated from the agent is separated from the reducing agent so that the reducing agent so that the electrons must travel through a electrons must travel through a wire from reducing agent to wire from reducing agent to oxidizing agentoxidizing agent
Electrochemical Electrochemical battery (galvanic cell) battery (galvanic cell) Reducing agent loses electrons so Reducing agent loses electrons so
it is oxidizedit is oxidized Electrode where oxidation occurs Electrode where oxidation occurs
is called the anodeis called the anode Oxidizing agent gains electrons Oxidizing agent gains electrons
and is reducedand is reduced Electrode where reduction occurs Electrode where reduction occurs
is the cathodeis the cathode
Figure 18.5: Schematic of a Figure 18.5: Schematic of a battery.battery.
Electron flow anode to cathode
oxidation to reduction
Anode - electrode where oxidation occurs
Cathode – electrode where reduction occurs
ElectrochemistryElectrochemistry
Go back to first cell with Zn and Cu and draw a voltaic cell. Label anode, cathode, and show direction of e- flow. Write out the two half reactions and then write out the complete reaction.
Cu/Zn Voltaic CellCu/Zn Voltaic Cell
CuCu2+2+ + 2e- + 2e- Cu Cu Cathode/reductionCathode/reduction
Zn Zn Zn Zn2+ 2+ + 2e- + 2e- Anode/oxidationAnode/oxidation
CuCu2+2+ + Zn + Zn Zn Zn2+ 2+ + Cu+ Cu
Zn2+Cu2+
ZnCu
SO42-
Zn2
+
ElectrochemistryElectrochemistry