What is an adsorption isotherm? Describe Freundlich adsorption isotherm?

Adsorption isotherm is the variation of the mass of the gas (adsorbate) adsorbed per gram of the adsorbent with pressure at constant temperature.The Freundlich adsorption isotherm is the mathematical representation for the variation of the extent of adsorption (\\(x/m\\)) with pressure (\\(P\\)) at a given temperature. Here, \\(x\\) is the mass of adsorbate and \\(m\\) is the mass of adsorbent. The expression is \\(\displaystyle \dfrac {x}{m} =k\times P^{\dfrac {1}{n}}\\),

Why does physisorption decrease with the increase of temperature?

Physisorption is exothermic in nature. Therefore in accordance with the Le-Chatelier principle, it decreases with an increase in temperature. This means physisorption occurs at a low temperature more readily.Physisorption is reversible in nature.

Why is adsorption always exothermic?

\\(Explanation:\\) The surface particle of any substance is active. They try to adsorb other molecules/atoms on it to become stable. When molecule/atoms get adsorb on the surface of the adsorbent, it becomes stable and releases energy. During adsorption, energy is released due to the presence of attraction between adsorbate and adsorbent molecules. Therefore, adsorption is always exothermic.

What is the difference between physisorption and chemisorption?

Physisorption (Physical adsorption)Chemisorption (Chemical adsorption) Weak van der Waals forces are present between the adsorbate molecules and the adsorbent.Strong chemical forces similar to chemical bonds are present between the adsorbate molecules and the adsorbent.The enthalpy of adsorption is low (20 to 40 kJ/mol).The enthalpy of adsorption is high (40 to 400 kJ/mol). Occurs at low temperature and decreases with an increase in temperature. Occurs at high temperature and increases with increase in temperature. It is reversible.It is irreversible. No significant activation energy is required.Usually, high activation energy is required. It forms multimolecular layers.It forms unimolecular layers.

According to Freundlich adsorption isotherm, which of the following is correct?

Correct Option : \\(D\\)Hint: Apply the concept that the adsorption isotherm given by Freundlich depends on the amount of pressure and changes accordingly.Explanation:According to Freundlich’s adsorption isotherm,\\(\dfrac{x}{m}\propto p^{\dfrac{1}{n}}\\), where \\(n>1\\).Here, \\(p\\) is the pressure at equilibrium and \\(\dfrac{x}{m}\\) is the mass of gas adsorbed per unit mass of the adsorbent substance.Let us have a look at the three situations.Case I: At low pressure, the formula can be written as:\\(\dfrac{x}{m}=Kp\\) (where, \\(K\\) is an arbitrary constant)Case II: At high pressure,\\(\dfrac{x}{m}\\) becomes almost constant and reaches its saturation value.\\(\dfrac{x}{m}=K\\) Case III: At intermediate range of pressure,\\(\dfrac{x}{m}\\)will depend mostly on the power of pressure which lies between \\(0\\) and \\(1\\) and is expressed as: \\(\dfrac{x}{m}=K.p^{\dfrac{1}{n}}\\)Hence, all three options are used in Freundlich's adsorption isotherm. Correct Option: \\(D\\)

Distinguish between chemical and physical adsorption.

Physical adsorptionChemical adsorption Weak van der Waals forces are present between adsorbate and adsorbent.Strong chemical (covalent) bonds are formed between adsorbate and adsorbent. It has low heat of adsorption (20 to 40 kJ/mol). It has high heat of adsorption (40 to 200 kJ/mol). Multilayers of adsorbed particles are formed.Monolayer of adsorbed particles is formed. It is not specific in nature. It is specific in nature.

Which of the following is not characteristic of chemisorption?

Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface.Various characteristics of Chemisorption are-High specificity: Chemisorption is highly specific and it will only occur if there is some possibility of chemical bonding between adsorbent and adsorbate.It is irreversible in nature.Surface area: Chemisorption increases with the increase of the surface area of the adsorbent.Enthalpy of adsorption: Enthalpy of chemisorption is high (\\(80-240 \\)\\(kJ\\) \\(mol^{-1}\\))) as it involves chemical bond formation.Chemisorption doesn't form multimolecular layers and hence option D is a correct answer.

The plot of\\(\log x/m\\) against \\(\log p\\) is a straight line inclined at an angle of \\(45^{\circ}\\). When the pressure is \\(0.5\ atm\\) and Freundlich parameter, \\(k\\) is \\(10\\), the amount of solute adsorbed per gram of adsorbent will be: \\((\log 5 = 0.6990)\\)

The Freundlich adsorption isotherm is mathematically expressed as:\\(\dfrac xm = KP^{\cfrac1n}\\)It can be written in \\(y=mx+c\\)\\(\log\cfrac{x}{m}=\dfrac{1}{n}\times \log P+\log K\\)\\(\log\cfrac{x}{m}= \dfrac{1}{n}\log (0.5)+\log (10)\\)Therefore, plot of \\(log \dfrac{x}{m}\\) vs \\(log\ P\\) is a straight line with slope = \\(\dfrac{1}{n}\\) and intercept = log KThus ,\\(\dfrac{1}{n} = tanθ = tan45^{0} =1 \\)\\( n=1\\)\\(\log \cfrac{x}{m}=\log 5-\log (10)+\log (10)\\)\\(\log \cfrac{x}{m}=\log 5\\)\\(\cfrac{x}{m}=5\\)Hence amount of solute per gram is \\(5g\\).

For adsorption \\(\Delta G, \Delta S\\) and \\(\Delta H\\) all have negative values.

Adsorption is a spontaneous process accompanied by decrease in randomness.

Adsorption of a gas follows Freundlich adsorption isotherm \\(x\\) is the mass of the gas adsorbed on mass \\(m\\) of the adsorbent. The plot of log \\(\dfrac{x}{m}\\) versus log \\(p\\) is shown in the given graph. \\(\dfrac{x}{m}\\) is proportional to :

Solution:- (C) \\({p}^{{2}/{3}}\\)\\(\dfrac{x}{m}=K.p^{1/n}\\)\\(\therefore log \dfrac{x}{m}=log K+\dfrac{1}{n}. log P\\)slope \\(=\dfrac{1}{n}=\dfrac{2}{3}\\)\\(\therefore \dfrac{x}{m}=K.p^{2/3}\\)

Adsorption | Definition, Examples, Diagrams

definition

Adsorbate

A material that has been or is capable of being adsorbed is known as adsorbate.
e.g Oxygen molecule adsorbed on cobalt. Here oxygen is adsorbate.

definition

Adsorbent

The substance on which adsorbate is adsorbed is called adsorbent. Major types of adsorbents in use are: activated alumina, silica gel, activated carbon, molecular sieve carbon, molecular sieve zeolites and polymeric adsorbents. Most adsorbents are manufactured (such as activated carbons), but a few, such as some zeolites, occur naturally.

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Mechanism of adsorption

Adsorption occur when the surface particles of the adsorbent experience the unbalanced attractive forces from the bulk, but on the surface the particles are not surrounded by atoms or molecules from all side. Hence, they possess unbalanced attractive forces. These forces of the adsorbent are responsible for attracting the adsorbate particles on its surface.
Adsorption increase with increase in surface area per unit mass of the adsorbent at a given temperature and pressure.

definition

Exothermic nature of adsorption and the entropy change

When adsorption takes place, surface energy decreases. This appears in the form of heat of adsorption. Hence, adsorption is invariably an exothermic process,i.e

Δ H_{a d s o r p t i o n}

is always negative.

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Difference between adsorption and absorption

Adsorption	Absorption
It is a surface phenomenon	It is a bulk phenomenon
The concentration on the surface of adsorbent is different from that in the bulk	The concentration is same throughout
Its rate is high in the beginning and then decreases	It remains same throughout the process

definition

Adsorption

Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. They are of two types: Physisorption and Chemisorption, e.g., oxygen molecules (red) adsorbed on a bimetallic surface of platinum (purple) and cobalt (green).

A material that has been or is capable of being adsorbed is known as adsorbate.
Example- Oxygen molecule adsorbed on cobalt. Here oxygen is adsorbate.

The substance on which adsorbate is adsorbed is called adsorbent
Major types of adsorbents in use are activated alumina, silica gel, activated carbon, molecular sieve carbon, molecular sieve zeolites, and polymeric adsorbents.

definition

Sorption

When both adsorption and absorption take place simultaneously. The term sorption is used.
e.g: Dyes get adsorbed as well as absorbed in the cotton fibres.

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Factors affecting adsorption of gases by solids

Nature and surface area of the absorbent
Nature of the gas being adsorbed
Temperature
Pressure
Activation of the solid adsorbent

definition

Heat of adsorption

The amount of heat evolved when 1 mole of the gas is adsorbed on the adsorbent is called heat of adsorption.

Adsorption

definition

Adsorbate

definition

Adsorbent

definition

Mechanism of adsorption

definition

Exothermic nature of adsorption and the entropy change

definition

Difference between adsorption and absorption

definition

Adsorption

definition

Sorption

definition

Factors affecting adsorption of gases by solids

definition

Heat of adsorption

REVISE WITH CONCEPTS

Types of Adsorption

Adsorption Isotherms

Applications of Adsorption

Quick Summary With Stories

Introduction to Adsorption

What is an adsorption isotherm? Describe Freundlich adsorption isotherm?

Why does physisorption decrease with the increase of temperature?

Why is adsorption always exothermic?

What is the difference between physisorption and chemisorption?

According to Freundlich adsorption isotherm, which of the following is correct?

Distinguish between chemical and physical adsorption.

Which of the following is not characteristic of chemisorption?

The plot of $lo g x / m$ against $lo g p$ is a straight line inclined at an angle of $4 5^{\circ}$ . When the pressure is $0.5 a t m$ and Freundlich parameter, $k$ is $10$ , the amount of solute adsorbed per gram of adsorbent will be: $(lo g 5 = 0.6990)$

For adsorption $Δ G, Δ S$ and $Δ H$ all have negative values.

Adsorption is a spontaneous process accompanied by decrease in randomness.

Adsorption of a gas follows Freundlich adsorption isotherm $x$ is the mass of the gas adsorbed on mass $m$ of the adsorbent. The plot of log $\frac{x}{m}$ versus log $p$ is shown in the given graph. $\frac{x}{m}$ is proportional to :

definition

Adsorbate

definition

Adsorbent

definition

Mechanism of adsorption

definition

Exothermic nature of adsorption and the entropy change

definition

Difference between adsorption and absorption

definition

Adsorption

definition

Sorption

definition

Factors affecting adsorption of gases by solids

definition

Heat of adsorption

REVISE WITH CONCEPTS

Types of Adsorption

Adsorption Isotherms

Applications of Adsorption

Quick Summary With Stories

Introduction to Adsorption

What is an adsorption isotherm? Describe Freundlich adsorption isotherm?

Why does physisorption decrease with the increase of temperature?

Why is adsorption always exothermic?

What is the difference between physisorption and chemisorption?

According to Freundlich adsorption isotherm, which of the following is correct?

Distinguish between chemical and physical adsorption.

Which of the following is not characteristic of chemisorption?

The plot oflogx/m against logp is a straight line inclined at an angle of 45∘. When the pressure is 0.5 atm and Freundlich parameter, k is 10, the amount of solute adsorbed per gram of adsorbent will be: (log5=0.6990)

For adsorption ΔG,ΔS and ΔH all have negative values.

Adsorption is a spontaneous process accompanied by decrease in randomness.

Adsorption of a gas follows Freundlich adsorption isotherm x is the mass of the gas adsorbed on mass m of the adsorbent. The plot of log mx​ versus log p is shown in the given graph. mx​ is proportional to :

The plot of $lo g x / m$ against $lo g p$ is a straight line inclined at an angle of $4 5^{\circ}$ . When the pressure is $0.5 a t m$ and Freundlich parameter, $k$ is $10$ , the amount of solute adsorbed per gram of adsorbent will be: $(lo g 5 = 0.6990)$

For adsorption $Δ G, Δ S$ and $Δ H$ all have negative values.

Adsorption of a gas follows Freundlich adsorption isotherm $x$ is the mass of the gas adsorbed on mass $m$ of the adsorbent. The plot of log $\frac{x}{m}$ versus log $p$ is shown in the given graph. $\frac{x}{m}$ is proportional to :