Associate Safety Professional Practice Exam

If a material with a molecular weight of 90 evaporates from an enclosed process tank, where would it accumulate?

1. On the roof

2. In the atmosphere

3. On the floor

4. In the ventilation system

The correct answer is: On the floor

When considering the evaporation of a material with a molecular weight of 90, it's important to understand the behavior of vapors in enclosed spaces. Generally, lighter gases tend to rise due to their lower density compared to air, which is a mix of heavier molecules predominantly made up of nitrogen and oxygen. However, molecular weight is just one aspect to consider. The specific properties of the substance, such as its vapor density compared to air, also play a significant role in determining where it accumulates. For a substance with a molecular weight of 90, if it is less dense than air, it may ascend and potentially collect at higher elevation points, such as the roof of the tank or building. Given these considerations, it's possible that the weight takes on a certain behavior under specific conditions. However, if the environment is entirely enclosed and if ventilation isn't present or is not effective, a heavier vapor might also settle towards the floor, particularly if the substance does not disperse evenly or if minimal movement is occurring within the space. Thus, while a material with a molecular weight of 90 might be expected to have vapor that tends to rise, due to particular characteristics of how it interacts with air in that closed environment, it is plausible that it could accumulate at the