JEE Main · 2022 · 28 Jul 2022 · Shift 2 · Surface Chemistry

The Freundlich adsorption isotherm is given by: $\frac{x}{m}=k{P}^{1/n}$

Taking logarithm: $\log \frac{x}{m}=\frac{1}{n}\log P+\log k$

This represents a straight line with positive slope $\frac{1}{n}$ when $\log \frac{x}{m}$ is plotted against $\log P$.

For a plot of $\frac{x}{m}$ vs $P$, the curve should show:

• Initial steep rise (at low pressure)
• Gradual flattening at higher pressure (saturation)
• Never decreasing or showing maxima/minima

Examining the four curves:

• Curve (a): Shows a maximum and then decrease — NOT in accordance
• Curve (b): Shows typical Freundlich behavior — in accordance
• Curve (c): Shows decrease throughout — NOT in accordance
• Curve (d): Shows oscillation/wave pattern — NOT in accordance

Therefore, 3 curves are not in accordance with Freundlich isotherm.