Consider the well-documented adsorption of nitrogen gas () onto a finely divided iron surface. Which — Surface Chemistry Chemistry Question

💡 Solution & Explanation

Statements A and B are factual observations confirmed in standard texts; $N_2$ physisorbs on Fe at moderate/low temps ($463\text{ K}$) and chemisorbs at high temps ($723\text{ K}$). Statement C is false; chemisorption has a much *higher* magnitude of heat of adsorption ($40-400\text{ kJ/mol}$) compared to physisorption ($<40\text{ kJ/mol}$). Statement D correctly explains why chemisorption occurs at high temperatures (it is an activated process requiring bond cleavage).