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MCAT General Chemistry Review 7
Lesson 7 - Electrochemistry
25
Chemistry
Not Applicable
07/04/2011

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Term
Oxidation-Reduction Reaction (Redox Reaction)
Definition
Electrons are transferred from one atom to another.
Term
Oxidation
Definition

An atom that loses an electron

 

Λ H+

Λ O

V Electron

Term
Reduction
Definition

Atom gains an electron

 

Λ electrons

V H+

V O

Term
Oxidation State
Definition
The possible charge values that an atom may hold within a molecule.
Term
Oxidation States
Definition

0 : Atoms in elemental form

-1: Flourine

+1: Hydrogen (except when bonded to a metal when it is -1)

-2: Oxygen (Except when peroxide)

+1: Group 1

+2: Group 2

-3: Group 15

-2: Group 16

-1: Group 17 (Halogens)

 

Term
Reducing Agent
Definition
Gives the electron to an atom and is oxidized.
Term
Oxidizing Agent
Definition
Atom that is received the electron and be reduced.
Term
Electric Potential, E
Definition
Charge transfer resulting from a redox reaction
Term
Half Reaction
Definition
One component of a redox reaction
Term
Reduction Potential
Definition
Half reaction potential
Term
Galvonic Cell (Voltaic Cell)
Definition
Uses the electric potential between phases in a redox reaction to generate a current of electrons from one phase to another in a conversion of chemical energy to electrical energy.
Term
Salt Bridge
Definition

Ionic conducting phase of a Galvonic Cell.

Impermeable to electrons.

Term
Terminals
Definition
Electron Conductors such as metal wires.
Term
Electrodes
Definition

Electronic conductors of a galvonic cell.

Cathode and Anode.

Term
Anode
Definition

Marked with a negative sign.

 

Oxidation half reaction occurs here.

Term
Cathode
Definition

Marked with a positive sign.

 

Location of the reduction half reaction.

Term
Cell potential, E (Electromotive force)
Definition
The potential difference between the terminals when they are not connected.
Term
Free Energy
Definition

ΔG=-nFEmax

 

n=moles

F = Faraday's Constant (96,486 C mol-1)

E = voltage

 

-ΔG = work done by system, not on the system

+ΔG = work done on the system

Term
Non standard-state ΔG
Definition

ΔG=ΔGO+RTln(Q)

 

Q=reaction quotient

ΔGO=Standard State ΔG

 

Term
Free Energy at Equilibrium
Definition

ΔGO=-RTln(K)

 

If K=1, ΔGO=0

If K > 1, ΔGO<0

If K<1, ΔGO>0 

Term
Concentration Cell
Definition

A limited form of a galvonic cell with a reduction half reaction taking place in one half cell and the exact reverse of that half reaction taking place in the other half of the cell.

 

Never at standard conditions, so the Nernst equation is needed to solve for the cell potential.

Term
Electrolytic Cell
Definition

A galvonic cell with the power hooked up forcing the cell to run backwards.

 

Negative emf.

 

cathode is negative, anode is positive.

reduction still occurs on cathode and oxidation on anode.

 

used for metal plating and purifying.

plating occurs on the cathode.

Term
Current
Definition
I = Q/t
Term
Positive reduction potential
Definition
Will be reduced
Term
Negative Reduction potential
Definition
Will be oxidized.
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