How much vacuum is needed to obtain a clean surface of metal?

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: $\ln 10 = 2.3$,$R = 8.3 \ J \ K^{-1} \ mol^{-1}$.

What is the difference between adsorbent and adsorbate?

The correct order of adsorption of the following gases on the surface of charcoal is: $H_2$ $(I)$,$CH_4$ $(II)$,$SO_2$ $(III)$.

The validity of the Freundlich isotherm can be verified by plotting:

Assertion : The enthalpy of physisorption is greater than chemisorption.
Reason : Molecules of adsorbate and adsorbent are held by van der Waal's forces in physisorption and by chemical bonds in chemisorption.