surface chemistry

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Safa

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adsorption is a surface phenomenon whereas absorption is a completely bulk/core phenomenon.
concentration in adsorption is not homogenetic whereas the concentration in absorption is same throughout the substance.
an example of adsorption is silica gel adsorbing moisture.
an example of absorption is anld. cacl2 absorbing h2o
a promoter is a substance which increases the activity of the catalyst
example molybdenum is a promoter for iron catalyst
A substance which decreases the activity of the catalyst is called as poison.
example: carbon monoxide acts as a poison for iron catalyst in haber's process.
a substance which alters the rate of chemical reaction without itself being consumed by the process is called as catalysis
if the reactants and the catalyst are in the same physical state in a reaction it is called as homogenous catalysis
if the reactants and catalyst are in different physical state in a reaction it is called as heterogenous catalyst
in some reactions one of the product formed itself acts as a catalyst which is called as an autocatalyst and this phenomenon is called as autocatalysis
the phenomenon where the enzyme acts a a catalyst is called as enzyme catalyst
Colloids are of two types based on the interaction between the dispersed phase and dispersion medium: lyophilic colloids and lyophobic colloids
Lyophilic colloids have a very strong interaction between the dispersion medium and dispersion phase
Lyophobic colloids have a weak interaction between the dispersion medium and dispersion phase
Lyophilic colloids are highly stable, while lyophobic colloids are not stable
Lyophilic sols are reversible, whereas lyophobic sols are irreversible sols
Lyophilic colloids are prepared by simple methods that require no chemical reaction
Lyophobic colloids are prepared by special methods that involve chemical reactions
Example of a lyophilic sol is starch sol
Example of a lyophobic sol is Fe(OH)2 sol
Zeolites are shape selective catalysts
zeolites are porous and have 3D network of silicates in which some of the silicon atoms are replaced by aluminum atoms
The catalytic activity of zeolites depend on its pore size and shape and size of reactant and the product molecules
One of the examples of zeolites is zsm-5 which catalyses alcohol to gasoline.
in the oxidation of oxalic acid with acidified KMNO4, Mn^+2 ion acts as an autocatalyst.
Adsorption is of two types: Physical adsorption and Chemical adsorption
In physical adsorption, weak wanderwaal force is present between the adsorbent and adsorbate
In chemical adsorption, strong chemical bond takes place between the adsorbent and adsorbate
Enthalpy of physical adsorption is low
Enthalpy of adsorption is high in chemical adsorption
Physical adsorption is not specific in nature
Chemical adsorption is highly specific in nature
Physical adsorption does not require any activation energy
Chemical adsorption requires chemical energy
Physical adsorption is reversible
Chemical adsorption is irreversible
With an increase in temperature, physical adsorption decreases
With an increase in temperature, chemical adsorption increases
Physical adsorption involves multi molecular layer formation
Chemical adsorption involves only uni molecular layer formation
A graph between pressure and extent of adsorption (x/m) is called as adsorption isotherm.
the relation between the extent of adsorption and pressure is given by Freundlich adsorption isotherm
$x/m ∝ p^1/^m$
$x/m =$ $Kp^1/^m$