If a substance is in a container designed to hold anhydrous ammonia, it is presumed to be what?

The presumption that a substance within a container designed to hold anhydrous ammonia is ammonia itself is based on the specific design and intended use of the container. These containers are specifically engineered to safely hold anhydrous ammonia due to its unique properties, such as being a colorless gas with a pungent odor and the potential to become a liquid under pressure.

Materials that can be placed in such containers are typically limited to those that can handle the chemical's characteristics safely. Containers intended for anhydrous ammonia provide crucial information about their intended contents; therefore, if the container is labeled or designed for anhydrous ammonia, it is reasonable and generally accepted to presume that the substance within is ammonia.

In contrast, other substances or options do not cohere with the specific usage of these specialized containers. Containers for anhydrous ammonia would not be used for water or arbitrary gases that do not have similar chemical handling requirements. Thus, the correct identification of the contents based on the container's design directly leads us to conclude that the substance is ammonia.