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WRITTEN BY NITHIN
SURFACE
CHEMISTRY
GEENU TEACHER
WRITTEN BY
NITHIN
ADSORPTION
It is the accumulation of molecules of a substance on the surface of a liquid or a
solid than the bulk
...
ADSORBATE: The substance that gets adsorbed or attached
...
DESORPTION: It is the removal of adsorbate from the surface of adsorbent
...
It is a bulk phenomenon
...
surface
...
slowly decreases
...
ENTHALPY AND ENTROPY CHANGES DURING ADSORPTION
During adsorption , there is a decrease in surface energy and it appears as heat
...
When a gas is adsorbed
the freedom of its molecules is reduced and hence entropy of the gas is decreased
...
For a process to be spontaneous βG must be negative
...
So
adsorption is spontaneous at low temperature
...
At this stage equilibrium will be attained
...
COMPARISION BETWEEN PHYSISORPTION AND CHEMISORPTION
PHYSICAL ADSORPTION
CHEMICAL ADSORPTION
Caused by intermolecular Vander waalβs
Caused by chemical bond formation
...
It is not specific
...
It is reversible
...
Heat adsorption is low(20-40KJ/mol)
High heat of adsorption(80-240KJ/mol)
Low temperature is favourable
...
Results multilayer adsorption
...
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WRITTEN BY
NITHIN
ADSORPTION ISOTHERMS
The variation in the amount of gas absorbed by the adsorbent with pressure at constant
temperature can be expressed by means of a grap called adsorption isotherm
...
π₯
π
=K
Where K-Constant, n-Integer>unit, x and m-masses of
adsorbate and adsorbent
...
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WRITTEN BY
NITHIN
ADSORPTION
FROM
SOLUTION
Solid
adsorbents
adsorb certain
solutes from
solutions in
preference to
other solutes
and solvents
...
For solutions, the equation takes in the form,
πππ
π₯
1
= log πΎ + ππππΆ
π
π
APPLICATIONS OF ADSORPTION
In the production of high vaccum
...
In the control of humidity
...
In heterogenous catalysis
...
In curing diseases
...
Adsorption indicators
...
COLLOIDS
Colloid is an intermediate state between true solution and suspension
...
TYPES OF COLLOIDAL SYSTEMS BASED ON NATURE OF DISPERSION MEDIUM
DISPERSION MEDIUM
NAME OF COLLOID
AIR
AEROSOL
WATER
HYDROSOL
Page 4|6
WRITTEN BY
NITHIN
BENZENE
ALCOHOL
BENZOSOL
ALCOSOL
TYPES OF COLLOIDAL SYSTEMS BASED ON PHYSICAL STATE
DISPERSED PHASE
DISPERSION
TYPE OF COLLOID
MEDIUM
SOLID
SOLID
SOLID SOL
SOLID
LIQUID
SOL
SOLID
LIQUID
LIQUID
LIQUID
GAS
GAS
SOLID
LIQUID
GAS
SOLID
AEROSOL
GEL
EMULSION
AEROSOL
SOLID SOL
GAS
LIQUID
FOAM
EXAMPLES
COLORED GLASSES,
ALLOYS
PAINT, MUDDY
WATER
SMOKE, DUST
CHEESE, BUTTER
MILK, HAIR CREAM
FOG, CLOUD, MIST
FUMICE STONE,
FOAM , RUBBER
FROTH, WHIPPED
CREAM
TYPES OF COLLOIDAL SYSTEMS BASED ON NATURE OF INTERACTION
LYOPHILLIC COLLOIDS
SOLVENT LOVING
REVERSIBLE
STABLE
PREPARED FROM ORGANIC MATERIAL
EASILY PREPARED
SELF STABILIZED
Eg: STARCH, GELATINE
LYOPHOBIC COLLOIDS
SOLVENT HATING
IRREVERSIBLE
UNSTABLE
PREPARED FROM INORGANIC MATERIAL
CANNOT BE EASILY SEPARATED
NOT SELF STABILIZED
Eg: METAL HYDROXIDES
TYPES OF COLLOIDAL SYSTEMS BASED ON NATURE OF PARTICLES
1
...
Eg: Gold sol, Sulphur Sol
...
MACROMOLECULAR COLLOIDS
In this types of colloids, colloidal particles are themselves large molecules of
colloidal dimension
...
3
...
Such colloids are called associated colloids and the associated
particles are called micelles
...
The formation of micelles takes place only above a particular temperature called
kraft temperature and above a particular concentration called critical micelle
concentration (CMC)
...
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