Adsorption

During adsorption entropy decreases, so $\Delta S < 0$.
$\Delta G = \Delta H - T\Delta S$
For spontaneous adsorption $\Delta G < 0$, so $\Delta H$ should be highly negative.

$\frac{x}{m} = f(p)$ at constant T is the adsorption isotherm (e.g., Freundlich isotherm $\frac{x}{m} = kp^{1/n}$).
$\frac{x}{m} = f(T)$ at constant p is the adsorption isobar.
$p = f(T)$ at constant $\frac{x}{m}$ is the adsorption isostere.
$\frac{x}{m} = p\times T$ would mean that adsorption increases in direct proportion to both pressure and temperature. This is not true: adsorption is exothermic and decreases with rise in temperature.
Hence the relation not related to adsorption is $\frac{x}{m} = p\times T$.