Four idealised gases, A, B, C, and D, have critical temperatures of , , , and , respectively. Assumi — Surface Chemistry Chemistry Question
Question
Four idealised gases, A, B, C, and D, have critical temperatures of $33\text{ K}$, $126\text{ K}$, $190\text{ K}$, and $430\text{ K}$, respectively. Assuming only physical adsorption takes place, which gas will show the greatest extent of adsorption on $1\text{ g}$ of activated charcoal under identical moderate conditions of temperature and pressure?
💡 Solution & Explanation
The critical temperature of a gas is a direct measure of the strength of its intermolecular van der Waals forces. Gases with higher critical temperatures (like Gas D, $430\text{ K}$) are more easily liquefiable because of stronger intermolecular attractions. Since physisorption relies on these exact same forces, a higher critical temperature results in a greater extent of physical adsorption.