Unit 5B - Galvanic & Electrolytic Cells - AP Chemistry

electrochemistry

electrochemistry

using chemical (redox) reactions to produce electricity or vice-versa

galvanic/voltaic cell

a chemical apparatus that uses an electrochemical reaction to produce electricity (ex. battery)

atoms from anode

are oxidized and become part of the solution

ions from the solution

are reduced and become part of the cathode

oxidation reaction (formula)

X —> X+ + e-

reduction reaction (formula)

e- + Y —> Y-

entropy

disorder, less energy required

half cell

either of the two halves of a galvanic cell

electrode

a solid metal strip where either oxidation or reduction occurs

the metal strips also conduct the electrons into or out of the electric circuit

salt bridge

a salt solution that is connected to both half cells

provides ions for the two half-cells to keep the charges balanced

a salt bridge must be made of

ions that do not take part in the reactions at the cathode or anode

anode

the negatively (-) charge electrode

oxidation happens at the

anode

reduction happens at the

cathode

the anode, as metal ions become part of the solution

loses mass

cathode

the positively (+) charged electrode

reduction happens at the

cathode

the cathode, as metal ions become apart of it

gains mass

the electrical current in a galvanic cell moves through the wire and to

the cathode

electrolytic cell

a cell similar to a galvanic cell, except that the reaction is nonspontaneous, and electricity is used to add the energy needed to make the reaction occur

standard voltage (E°)

the voltage (electric potential) of an electrochemical reaction in which all ion concentrations are 1M and all gas pressures are 1 atm, as well as temp @ 25 dg C

a negative E° means

the reaction is not spontaneous

a positive E° means

the reaction is spontaneous

voltage depends on

the concentration of ions in solution

electroplating

using an electrolytic cell to add a layer of metal to a cathode

reduces metal ions from the solution which are then deposited onto the cathold

electric current

caused by the flow of electrons (measured in amperes A) 1 A = 1 C

electrical charge (q)

measured in Coulombs C, one Faraday (F) is the charge in, Couloms, of one mole of electrons

1F =

96,500 C/mol

I =

q/t