1. CHEMICAL
POTENTIAL
P R E S E N T E D TO : D R . S H A Z I A
P R E S E N T E D BY : M A R I A YA S M I N
R O L L N O. 7
2. INTRODUCTION
• Energy that can be absorbed or released due to a change of the particle number of the
given species.
• Also known as partial molar free energy.
• μa = ∆G/∆na
• Josiah Willard Gibbs.
• Chemical potential of a chemical substance, μ, can be simply defined as the chemical
energy possessed by 1 mol of the substance.
• Σμi ·= ∆G / ∆ni at constant T, P
3. IMPORTANCE OF CHEMICAL POTENTIAL
…1
• Raoult's law
• Mole Fraction
• xw + xs = 1
• xw = 1 - xs
• The change in chemical potential with pressure
= +RTlnXw
=
= +
= + + RTLn(xw)
4. CONTINUE…
• Using equation 1
• By putting the value of ‘Xw’
Π Vm = -RT ln(1-xs)
• When xs is low, the following approximation is valid
ln(1 - xs) = - xs
Π Vm = xsRT
• At low xs,
xs = ns/nw
Using equation 1
-RTLn(xw) = = Π Vm
5. CONTINUE…
• Given the volume of water (V),
V = nw ˣ Vm
• The molar concentration of the solute is
cs = ns/V = xsnw/nwVm = xs/Vm
• Put this value in eq. 4
Π = csRT
• Eq. 4 is
Π Vm = xsRT
Π /c = RT
Π /c = RT/Mn
6. PHYSICAL SIGNIFICANCE
• The tendency of a substance
to react with other substances,
to transform into another state,
to redistribute in space,
• The magnitude of this tendency, meaning the numerical value of µ is determined by
the
nature of the substance,.
• A reaction, transformation, redistribution, etc. can only proceed voluntarily if the
tendency for the process is more pronounced in the initial state than in the final state.
7. CHEMICAL POTENTIAL ENERGY AND LIFE
• It is the energy stored up in substances due to their chemical bonds. It is energy that
is stored in chemicals. One example of how this plays a part in real life is through
plants. The plants make energy with chemical potential energy by the process of
photosynthesis. Other organisms eat the plants to get energy and so on. Energy is
passed from one organism to another. This is how chemical potential energy works in
the environment. Another common example is the energy stored in gasoline. When
the car is turned on, the chemical energy in the gas is converted into mechanical
energy to move the car. The law of conservation of energy says energy cannot be
created or destroyed. It can only be changed from one form into another.
