What is the appearance of anhydrous ammonia?

Anhydrous ammonia is indeed a compressed liquid gas that is clear and colorless. Its physical state at room temperature and pressure is that of a gas, but it can be easily compressed into a liquid form. This characteristic is important in industrial refrigeration applications, where ammonia is used as a refrigerant. The clarity and colorlessness of anhydrous ammonia are key indicators of its purity and help in identifying it in various processes.

The other choices describe substances that do not accurately reflect the properties of anhydrous ammonia. For instance, a yellow liquid would indicate contamination or the presence of impurities, while a white crystalline solid suggests a different chemical compound altogether. An opaque green liquid does not align with the known characteristics of ammonia, which is utilized in many industrial settings, including refrigeration, due to its efficiency and effectiveness as a refrigerant. Understanding the true appearance of anhydrous ammonia is crucial for safety and effective handling in industrial applications.