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Why freundlich adsorption isotherm is not applicable at high pressure?
Wiki User
∙ 11y ago
Becoz at firstly as the pressure increases freundl. Isotherm is followed but at high pressure active sites are fully occupied.
Wiki User
∙ 11y ago
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What is the difference between the Freundlich and Langmuir adsorption isotherms?
ADSORPTION ISOTHERMA mathematical equation, which describes the relationship between pressure (p) of the gaseous adsorbateand the extent of adsorption at any fixed temperature, is called adsorption isotherm.The extent of adsorption is expressed as mass of the adsorbateadsorbed on one unit mass of the adsorbent.Thus, if x g of an adsorbateis adsorbed on m g of the adsorbent, thenExtent of adsorption =z/mVarious adsorption isotherms are commonly employed in describing the adsorption data.(1) Freundlichadsorption isotherm(i) Freundlichadsorption isotherm is obeyed by the adsorptions where the adsorbateforms a monomolecular layer on the surface of the adsorbent.x/m =kp1/n (Freundlichadsorption isotherm) orlog x/m =log k + 1/n log Pwhere x is the weight of the gas adsorbed by m gm of the adsorbent at a pressure p, thus x/m represents the amount of gas adsorbed by the adsorbents per gm (unit mass), k and n are constant at a particular temperature and for a particular adsorbent and adsorbate(gas), n is always greater than one, indicating that the amount of the gas adsorbed does not increase as rapidly as the pressure.(ii) At low pressure, the extent of adsorption varies linearly with pressure. x/m ∝ p'(iii) At high pressure, it becomes independent of pressure. x/m ∝ p0(iv) At moderate pressure x/m depends upon pressure raised to powers x/m ∝ p1/n(2) The Langmuir - adsorption isotherms(i) One of the drawbacks of Freundlichadsorption isotherm is that it fails at high pressure of the gas. Irving Langmuir in 1916 derived a simple adsorption isotherm, on theoretical considerations based on kinetic theory of gases. This is named as Langmuir adsorption isotherm.(a) Adsorption takes place on the surface of the solid only till the whole of the surface is completely covered with a unimolecularlayer of the adsorbed gas.(b) Adsorption consists of two opposing processes, namely Condensation of the gas molecules on the solid surface and Evaporation (desorption)ofthe gas molecules from the surface back into the gaseous phase.(c) The rate of condensation depends upon the uncovered (bare) surface of the adsorbent available for condensation. Naturally, at start when whole of the surface is uncovered the rate of condensation is very high and as the surface is covered more and more, the rate of condensation progressively decreases. On the contrary, the rate of evaporation depends upon the covered surface and hence increases as more and more of the surface is covered ultimately an equilibrium will be set up at a stage when the rate of condensation becomes equal to the rate of evaporation (adsorption equilibrium).(d) The rate of condensation also depends upon the pressure of the gas since according the kinetic theory of gases, the number of molecules striking per unit area is proportional to the pressure.Mathematically, x/m =ap/1+bp, where a and b are constants and their value depends upon the nature of gas (adsorbate),nature of the solid adsorbent and the temperature. Their values can be determined from the experimental data.Limitation of Langmuir theory(a) Langmuir's theory of unimolecularadsorption is valid only at low pressures and high temperatures.(b) When the pressure is increased or temperature is lowered, additional layers are formed. This has led to the modern concept of multilayer adsorption.
What are line connecting points of equal temperature?
The answer is very simple it's an isotherm map because an isobar map are lines that connect areas of the same pressure therefore lines that connect areas of the same temperature is and isotherm map
What connects locations of equal temperature?
Isotherm lines connect locationss of equal temperature on a weather map.The two parts of the word isotherm are: isomeaning "same" and therm meaning "temperature".(A similar construction is used for isobar, meaning a line of equal pressure.)
Isotherm in physics?
Isotherms in thermal physics are the lines on a pressure versus volume graph for an ideal gas, where the pressure and volume are alowwed to vary but temperature is kept constant. They are the result of Isothermal expansions or contracions of ideal gasses.
Explain how the national weather service makes weather maps?
The National Weather Service makes weather maps with special lines. Isotherm is a line that connects points of equal temperature. Isobar is a line that is drawn to connect equal atmosphere pressure.
What is Freundlich adsorption isotherm and Langmuir isotherm?
At a given temperature, the extent of adsorption will increase with the increase of pressure of the gas. The extent of adsorption is measured as x/m, where mi= is the mass of adsorbent and x that of adsorbate. At low pressure, x/m varies linearly with p. As per Freundlich adsorption equation Taking log both sides of the equation, we get, At low pressure, x/m=kP At high pressure, x/m=kPo This is called Freundlich adsorption isotherm at a constant temperature. Freundlich isotherm fails at high pressure and is only for physical adsorption. Langmuir isotherm is represented as x/m=ap/(1+bp) (a and b are constants) At very high pressure,(bp>>1) x/m=a/b At very low pressure,(bp<<1) x/m=ap
What are the disadvantages of Frenlich adsorption isotherm?
Frenlich adsorption isotherm has no theoretical basis. There are high chances of it failing when the concentration of the adsorbate is high. The equation is, usually, invalid at high pressure.
What is hill isotherm?
The Langmuir equation (also known as the Langmuir isotherm, Langmuir adsorption equation or Hill-Langmuir equation) relates the coverage or adsorption of molecules on a solid surface to gas pressure or concentration of a medium above the solid surface at a fixed temperature.
What is the difference between the Freundlich and Langmuir adsorption isotherms?
ADSORPTION ISOTHERMA mathematical equation, which describes the relationship between pressure (p) of the gaseous adsorbateand the extent of adsorption at any fixed temperature, is called adsorption isotherm.The extent of adsorption is expressed as mass of the adsorbateadsorbed on one unit mass of the adsorbent.Thus, if x g of an adsorbateis adsorbed on m g of the adsorbent, thenExtent of adsorption =z/mVarious adsorption isotherms are commonly employed in describing the adsorption data.(1) Freundlichadsorption isotherm(i) Freundlichadsorption isotherm is obeyed by the adsorptions where the adsorbateforms a monomolecular layer on the surface of the adsorbent.x/m =kp1/n (Freundlichadsorption isotherm) orlog x/m =log k + 1/n log Pwhere x is the weight of the gas adsorbed by m gm of the adsorbent at a pressure p, thus x/m represents the amount of gas adsorbed by the adsorbents per gm (unit mass), k and n are constant at a particular temperature and for a particular adsorbent and adsorbate(gas), n is always greater than one, indicating that the amount of the gas adsorbed does not increase as rapidly as the pressure.(ii) At low pressure, the extent of adsorption varies linearly with pressure. x/m ∝ p'(iii) At high pressure, it becomes independent of pressure. x/m ∝ p0(iv) At moderate pressure x/m depends upon pressure raised to powers x/m ∝ p1/n(2) The Langmuir - adsorption isotherms(i) One of the drawbacks of Freundlichadsorption isotherm is that it fails at high pressure of the gas. Irving Langmuir in 1916 derived a simple adsorption isotherm, on theoretical considerations based on kinetic theory of gases. This is named as Langmuir adsorption isotherm.(a) Adsorption takes place on the surface of the solid only till the whole of the surface is completely covered with a unimolecularlayer of the adsorbed gas.(b) Adsorption consists of two opposing processes, namely Condensation of the gas molecules on the solid surface and Evaporation (desorption)ofthe gas molecules from the surface back into the gaseous phase.(c) The rate of condensation depends upon the uncovered (bare) surface of the adsorbent available for condensation. Naturally, at start when whole of the surface is uncovered the rate of condensation is very high and as the surface is covered more and more, the rate of condensation progressively decreases. On the contrary, the rate of evaporation depends upon the covered surface and hence increases as more and more of the surface is covered ultimately an equilibrium will be set up at a stage when the rate of condensation becomes equal to the rate of evaporation (adsorption equilibrium).(d) The rate of condensation also depends upon the pressure of the gas since according the kinetic theory of gases, the number of molecules striking per unit area is proportional to the pressure.Mathematically, x/m =ap/1+bp, where a and b are constants and their value depends upon the nature of gas (adsorbate),nature of the solid adsorbent and the temperature. Their values can be determined from the experimental data.Limitation of Langmuir theory(a) Langmuir's theory of unimolecularadsorption is valid only at low pressures and high temperatures.(b) When the pressure is increased or temperature is lowered, additional layers are formed. This has led to the modern concept of multilayer adsorption.
Why physical adsorption is reversible process?
adsorption is processs of accumulation of liquid/gases on solid surface. reversible adsorption is seen in physical adsorption where increase in pressure increases the adsorption and decrease in pressure decrease adsorption of molecules to surface that is desorption takes place
What has the author Douglas M Ruthven written?
Douglas M. Ruthven has written: 'Pressure swing adsorption' -- subject(s): Adsorption
What line on a weather map indicates areas where the pressure is the sameness?
Isotherm. (apex)
Does pressure effect on adsorption of oxygen?
Yes. Pressue effects both adsorption and absorption of oxygen. I assume you really did mean adsorption (and not absorption) but just in case, this answer addresses both - since the answer is similar. As pressure increases, the fugacity of oxygen in the liquid or vapor phase will also increase. In order to stay in equilibrium, you would expect the concentration of oxygen on a surface (adsorption) to increase as well. There is one caveat in that if the oxygen is in a mixture, the fugacity of the other components of the mixture will also be increasing and may be in competition with the oxygen for adsorption to the surface. Once the surface is saturated, raising the pressure may not have any effect on the adsorption. Likewise, dropping the pressure will decrease the fugacity of oxygen in the fluid phase and promote desorption from a surface (the reverse of adsorption). Similarly, increasing or decreasing pressure will increase and decrease the fugacity of oxygen in the vapor phase and require more or less oxygen to be absorbed into a liquid (or in some cases solids - although most solids don't dissolve gasses very well). Increaing pressure can also change the distribution of oxygen between two immiscible liquids as the fugacity of the oxygen in each depends on both pressure and the effect of pressure on the fugacity of the solvent liquids.
What are line connecting points of equal temperature?
The answer is very simple it's an isotherm map because an isobar map are lines that connect areas of the same pressure therefore lines that connect areas of the same temperature is and isotherm map
What connects of equal temperature?
Isotherm lines connect locationss of equal temperature on a weather map.The two parts of the word isotherm are: isomeaning "same" and therm meaning "temperature".(A similar construction is used for isobar, meaning a line of equal pressure.)
BET surface area?
The specific surface area is usually calculated by using BET theory (including continuous flowing gas principle and static volumetric principle) from the gas adsorption isotherm data. The model of BET theory (using F-Sorb 2400CE, V-Sorb 2800P, V-Sorb 4800P methods) is that the adsorptive starts to adsorb on the strong energy sites on the surface first, and then, as the pressure is increased, the adsorptive adsorbs on the next energy level sites. The model also takes account of the 2nd, 3rd and higher layer adsorption.
What connects locations of equal temperature?
Isotherm lines connect locationss of equal temperature on a weather map.The two parts of the word isotherm are: isomeaning "same" and therm meaning "temperature".(A similar construction is used for isobar, meaning a line of equal pressure.)
