JEE Main · 2012 · 29 Apr 2012 · Offline · Surface Chemistry

The Freundlich isotherm $\frac{x}{m}=k{p}^{1/n}$ describes the general case, but the effective power of pressure changes with the range. At low pressure the uptake rises almost in direct proportion to pressure, so $\frac{x}{m}\propto p^1$; at very high pressure the surface saturates and the uptake becomes independent of pressure, $\frac{x}{m}\propto p^0$; in between it follows the fractional power $p^{1/n}$. All three forms are therefore correct, each over its own range of pressure.