2. Fundamentals

Electrochemistry

processes that influence the charge transfer across interfaces between chemical phases

One phase

is an electrolyte where charge is transported by ions

What form is one phase

solution, melt or an ionically conductive solid material)

The other phase

is often an electrode, but can be also another electrolyte, where charge is transported by electrons

What form is the other phase

metallic conductor, carbon, semiconductor).

How are electrochemical experiments conducted?

By applying :
- A constant electrical voltage/potential (E) ⇒ measure the resulting current (I)
- A constant current (I) ⇒ measure the resulting voltage/potential (E)

Potentiometry

the use of electrodes to measure voltages that provide chemical information

the working electrode is called

indicator electrode IE

An induced voltage is measured with a(n) ___.

high-input impedance voltmeter

Electric voltage... (E)

is the energy per unit charge gained or lost when a charge is moved from some reference point at which the potential is defined to be zero

Voltage

is the difference in potential between two (arbitrary) points at which the potential is not necessarily zero (vs. the reference point).

Electrical variables

Potetnial E
Currnt I
Charge Q

External Variables

Temperature (T)
Pressure (p)
Time (t)

Electrode variables

Material, surface area (A)
Geometry, surface condition

Solution variables

Bulk concentration of electroactive species (CO , CR)
Concentration of other species (electrolyte, pH)
Solvent

Mass transfer variables

Diffusion
Convection
Migration

Galvanic cell is without..

applied external voltage

Electrolytic cell is with...

applied external voltage

What is measured with a voltmeter with a high input impedance? the potential cannot be measured so what is done instead

Only the potential differences ∆E

Which cell has a Red Cat

The Galvanic Cell

Cell potential is calculated by...

the cathode and anodes reduction potentials
E^0

The redox couple with the higher standard potential X the redox couple with the lower standard potential.

oxidizes

The redox couple with the higher standard potential

will be the reduction reaction and the cathode

The redox couple with the lower standard potential

will be the oxidation reaction and the anode

The reaction is X if ΔG0 < 0

spontaneous

The charge Q is proportional to the....

moles of Zn that has been oxidized to Zn2+

The current I is proportional to the...

reaction rate

Faraday's Law equation

Q=nFN

Reaction rate equation

dN/dt =ν = I/nF

dN/dt in the reaction law

is the number of moles that reacts per time unit.

Power equation

P = E * I = U*I

Energy equation

P *t = E*I*t

Electrolysis involves

forcing a current through a cell to produce chemical reactions at the electrodes and decomposition of the materials.

Electrolysis of water

Water decomposes to hydrogen and oxygen gases