On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal?

Critical temperature is the maximum temperature at which a gas can be liquefied by applying high pressure. Higher the critical temperature of a gas, more easily it can be liquefied and adsorbed.

Here, H₂ gas has least value of critical temperature. So it shows least adsorption. So (iv) is correct.

Other gases, CO₂, SO₂ and CH₄ have relatively higher values of critical temperature. So they show higher rate of adsorption. So options (i),(ii) and (iii) are wrong.