What is the range of enthalpy of adsorption in physical adsorption? $(kJ \, mol^{-1})$

$A$ solid acts as an adsorbent because it has

For the adsorption of hydrogen on platinum,the activation energy is $30 \ kJ \ mol^{-1}$ and for the adsorption of hydrogen on nickel,the activation energy is $41.4 \ kJ \ mol^{-1}$. The logarithm of the ratio of the rates of chemisorption on equal areas of the metals at $300 \ K$ is $........$ (Nearest integer). Given: $\ln 10 = 2.3$,$R = 8.3 \ J \ K^{-1} \ mol^{-1}$.

Identify the example of sorption from the following.

Noble gases are adsorbed by

Which of the following compounds is formed when tungsten adsorbs oxygen gas?