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JEE Main Syllabus 2025 PDF - Subject Wise Topics

Freundlich Isotherm - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main

Quick Facts

  • Freundlich Isotherm is considered one the most difficult concept.

  • 12 Questions around this concept.

Solve by difficulty

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

For a linear plot of log(x/m) versus log(p) in a Freundlich adsorption isotherm, which of the following statements is correct?  (k and n are constants)

Concepts Covered - 0

Freundlich Isotherm

Freundlich adsorption isotherm:

Freundlich, in 1909, gave an empirical relationship between the quantity of gas adsorbed by unit mass of solid adsorbent and pressure at a particular temperature. The relationship can be expressed by the following equation:

\mathrm{\frac{x}{m}= k.p^{1/n}} (n>1)

where x is the mass of the gas adsorbed on mass m of the adsorbent at pressure P, k and n are constants which depend on the nature of the adsorbent and the gas at a particular temperature.

The relationship is generally represented in the form of a curve where mass of the gas adsorbed per gram of the adsorbent is plotted against pressure (Fig). These curves indicate that at a fixed pressure, there is a decrease in physical adsorption with increase in temperature. These curves always seem to approach saturation at high pressure.

Surface Chemistry Image 1

Logarithmic graph of Freundlich isotherm

Taking the logarithm of Eq. we get

\mathrm{log\frac{x}{m}= log\ k+\frac{1}{n}log\ p}

The validity of the Freundlich isotherm can be verified by plotting log(x/m) on the y-axis (ordinate) and log(p) on the x-axis (abscissa). If it comes to be a straight line, the Freundlich isotherm is valid, otherwise not (Fig.). The slope of the straight line gives the value of  \mathrm{\frac{1}{n}} . The intercept on the y-axis gives the value of log k.

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