Molecularity of an elementary reaction is defined as the number of reacting species (atoms, ions, or molecules) taking part in an elementary chemical reaction which must collide simultaneously in order to bring about a chemical reaction. In the decomposition of ammonium nitrite:

Only one reacting molecule is involved in the elementary decomposition, so the reaction is unimolecular and its molecularity is one (1).

Characteristics of physisorption:

• Non-specific: It arises from weak van der Waals forces, which exist between any gas and solid (correct characteristic).
• Low enthalpy: Because of weak forces, the enthalpy of physisorption is quite low, ranging only between $20 - 40\text{ kJ mol}^{-1}$. In contrast, chemisorption has high enthalpy of adsorption ($80 - 240\text{ kJ mol}^{-1}$). Therefore, stating that 'Enthalpy of adsorption is high' is NOT a characteristic of physisorption.
• Multimolecular layers: Under high pressure, gas molecules can form multiple layers on the solid surface (correct characteristic).

Nylon 6 is obtained by heating caprolactam with water at a high temperature ($533 - 543\text{ K}$):

Nylon 6,6 is made from adipic acid and hexamethylenediamine, while Dacron (terylene) is made from ethylene glycol and terephthalic acid.