AP Chemistry: Applications of Thermodynamics

electrochemistry

the study of chemical reactions that produce electricity and chemical reactions that take place because electricity is supplied

what are examples of electrochemical processes?

electroplating, electrolysis of water, production of aluminum metal, production and storage of electricity in batteries

what types of reactions are involved in electrochemical reactions?

redox reactions

why is indirect electron transfer needed for a redox reaction to produce energy?

no useful work can be done by the electrons

describe indirect electron transfer

two half reactions are physically separated and connected by the wire; electrons lost in oxidation flow through the wire to the reduction half

electrochemical cells

cells that use indirect electron transfer to produce electricity by a redox reaction, or use electricity to produce a desired redox reaction

galvanic (voltaic) cells

cells that produce electricity using a redox reaction

electrodes

portions of a cell that conduct electrons in the redox reaction

electrode compartments

solutions in which the electrodes are immersed

salt bridge

an inverted U-tube that holds a gel containing a concentrated electrolyte solution

why is a salt bridge needed in a galvanic cell?

to maintain electrical neutrality; otherwise, solutions will build up a postive or negative charge

anode

electrode at which oxidation takes place

anode compartment

electrolyte solution at which oxidation takes place

cathode

electrode at which reduction takes place

cathode department

electrolyte solution at which reduction takes place

in a galvanic cell, what are the signs of the anode and the cathode?

anodes are negative, cathodes are positive

inert (inactive) electrode

a solid conducting electrode that does not take part in the redox reaction

what are common inert electrodes?

graphite and platinum

cell notation

shorthand notation representing a galvanic cell

standard reduction potentials

the potential of a half-cell at 298 K with all components in their standard states and gases at 1 atm

standard cell potential

the potential (voltage) associated with a cell at standard conditions

the value of a standard cell potential for a galvanic cell must be

positive

the standard cell potential can be calculated by

substracting the standard cell potential of the cathode from the anode

electrolytic cells

cells using electricity from an external source to produce a desired redox reaction

what are some electrolytic cells?

electroplating and reacharging an automobile battery

electrolysis

decomposition of a compound with electricity

in an electrolytic cell, what are the signs of the anode and the cathode?

the anode is postiive and the cathode is negative

Faraday’s constant

96485 J/V mol

equation for Gibbs free energy of a reaction

delta G°=inFE°cell

equation for the equilibrium constant of a redox reaction

E=0.0592 V/n log K

Nernst equation

Ecell=Ecell°- RT/nF lnQ

what is the most common nonstandard condition?

the molarity is no longer 1 M

concentration cell

an electrochemical cell in which the same chemical species is used in both cell compartments

what instrument is used to measure cell potential?

voltmeter (potentiometer)