JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Surface Chemistry

The Freundlich isotherm is $\frac{x}{m}=k{p}^{1/n}$ with $n>1$, so adsorption rises with pressure but with a steadily falling slope rather than a straight line. Graph A, plotting $x/m$ against $p$, shows this curved rise that flattens at higher pressure, so it fits. Taking logarithms gives $\log \frac{x}{m}=\log k+\frac{1}{n}\log p$, a straight line of positive slope $1/n$ and intercept $\log k$, which graph B reproduces, so it fits. Graph D plots $x/m$ against $p^{1/n}$, which the isotherm makes a straight line through the origin, so it fits too. Graph C shows $x/m$ varying linearly with concentration, which the Freundlich equation does not predict, so it is excluded. The Freundlich isotherm is represented by A, B and D only.