What is the molecular weight (MW) of nitrous oxide?

• A. 22
• B. 36
• C. 44
• D. 56

Answer: (C)

Nitrous oxide, commonly known as laughing gas, has a molecular formula of N2O, consisting of two nitrogen atoms and one oxygen atom. To determine its molecular weight, we need to look at the atomic weights of its constituent elements.

The atomic weight of nitrogen is approximately 14.01 g/mol, and since there are two nitrogen atoms in the molecule, the contribution from nitrogen is 2 × 14.01 g/mol, which equals about 28.02 g/mol. The atomic weight of oxygen is approximately 16.00 g/mol. Adding these two contributions together results in a total molecular weight of about 28.02 g/mol (from nitrogen) + 16.00 g/mol (from oxygen) = 44.02 g/mol.

In rounding this to a commonly accepted molecular weight for nitrous oxide, it is typically stated as 44 g/mol. This value is crucial in anesthesia as it affects the pharmacokinetics and dynamics of nitrous oxide when used as an anesthetic agent.

This understanding of molecular weight is essential in various applications, including dosage calculations and understanding gas behavior in clinical settings.