The graph that correctly describes the absorption isotherms at two temperature T1 and T2 is given by option (d). According to Freundlich’s adsorption isotherm, the amount of the gas adsorbed is directly proportional to pressure applied raised to the power
1
n
.
x
m
∝p
1
n
[0<
1
n
<1] So, on increasing temperature,
x
m
decreases. ∴ Adsorption is basically exothermic in nature. Hence, correct option is (d).