Where would a material with a molecular weight of 90 accumulate if it evaporates from an enclosed process tank?

A material with a molecular weight of 90 is relatively low in comparison to many substances, meaning that it is likely to be lighter than air. When such a material evaporates from an enclosed process tank, it would primarily become a vapor.

In a closed space, the behavior of vapors generally depends on their density relative to air. Since the material is lighter than air, it tends to rise. However, the question involves the accumulation of this evaporated material. When a vapor rises, it may condense upon cooler surfaces or areas where airflow is restricted, which often happens near the floor when air circulation is limited.

Accumulation on the floor can also occur due to the gas cools down and settles after rising, particularly if there are surfaces or parts of the enclosure that facilitate this condensation process. Therefore, the correct answer emphasizes the tendency of the evaporated material to concentrate on the lower surfaces of the enclosed area where it can condense.