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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Chemistry
Chapter
Surface Chemistry

NTA Abhyas 2020 · Chemistry · Surface Chemistry

Which one is not correct according to Langmuir adsorption isotherm...

Which one is not correct according to Langmuir adsorption isotherm at very high pressure?

Options

  1. AIt is valid for chemisorption
  2. BIn \dfrac{X}{m} = - \dfrac{\Delta H^{o}}{RT} + \dfrac{\Delta S^{o}}{R}
  3. CXm=ab\dfrac{X}{m} = \dfrac{a}{b}
  4. DAt very high pressure rate of adsorption >> rate of desorption

Correct answer

D. At very high pressure rate of adsorption >> rate of desorption

Step-by-step solution

xm=ap1+bp\dfrac{x}{m} \text{=}\dfrac{\text{ap}}{\text{1}\text{+}\text{bp}}
at high pressure
1+bp≃bp\text{1}\text{+}\text{bp} ≃ \text{bp}
xm=apbp⇒xm=ab=constant\dfrac{x}{m} \text{=}\dfrac{\text{ap}}{\text{bp}} ⇒ \dfrac{x}{m} \text{=}\dfrac{a}{b} \text{=}\text{constant}
At very high P, rate of adsorption = rate or desorption
∴Xm=ab=const.(K)∴ \dfrac{X}{m} \text{=}\dfrac{a}{b} \text{=}\text{const}\text{.(K)}
∴ {\text{\Delta G}^{o} \text{=} - \text{2}\text{.303}\text\log\text{K}
or {\text{\Delta H}^{o} - {\text{T \Delta S}^{o} \text{=} - \text{2}\text{.303}\text\log\text{K}
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