What is the molecular weight of the substance?

To find the molecular weight of a substance, one must analyze its chemical composition. Each element contributes to the overall molecular weight based on the number of atoms and their respective atomic weights found on the periodic table.

If the correct answer is 17, it suggests that the molecular weight corresponds to a common compound such as ammonia (NH3), where nitrogen has a molecular weight of approximately 14 and each hydrogen atom has a weight of about 1, leading to a total of 14 (for nitrogen) + 3 (for hydrogen) = 17.

This highlights the importance of understanding molecular composition when calculating molecular weight. The other listed weights—18, 20, and 25—would pertain to different compounds or combinations of elements. For example, water (H2O) has a molecular weight of 18, but without the context of the specific substance intended by the question, indicating that 17 is a weight that is accurately aligned with ammonia. Understanding molecular weights is crucial in the field of refrigeration, where the properties of refrigerants directly impact system performance.