MCAT General Chemistry Review 7

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

An atom that loses an electron


Λ H+


V Electron


Atom gains an electron


Λ electrons

V H+


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

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)


Reducing Agent
Gives the electron to an atom and is oxidized.
Oxidizing Agent
Atom that is received the electron and be reduced.
Electric Potential, E
Charge transfer resulting from a redox reaction
Half Reaction
One component of a redox reaction
Reduction Potential
Half reaction potential
Galvonic Cell (Voltaic Cell)
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.
Salt Bridge

Ionic conducting phase of a Galvonic Cell.

Impermeable to electrons.

Electron Conductors such as metal wires.

Electronic conductors of a galvonic cell.

Cathode and Anode.


Marked with a negative sign.


Oxidation half reaction occurs here.


Marked with a positive sign.


Location of the reduction half reaction.

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




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

E = voltage


-;G = work done by system, not on the system

+;G = work done on the system

Non standard-state;;G



Q=reaction quotient

;GO=Standard State;;G


Free Energy at Equilibrium



If K=1,;;GO=0

If K ; 1,;;GO;0

If K;1, ;GO;0;

Concentration Cell

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.

Electrolytic Cell

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.

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

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