What is the density of air at standard temperature and pressure in kg/m³?

• A. 1.29
• B. 2.5
• C. 0.8
• D. 1.0

Answer: (A)

The density of air at standard temperature (0 degrees Celsius) and pressure (1 atmosphere) is approximately 1.29 kg/m³. This value represents the mass of air within a cubic meter at these specified conditions.

Understanding why this is the correct answer involves knowing that the density of a gas can vary based on factors like temperature and pressure. At standard conditions, the molecular composition of air, which is primarily nitrogen and oxygen, yields a density around 1.29 kg/m³.

This value is vital for calculations in various applications, including pipefitting, where understanding the properties of gases may be crucial when designing systems that transport air or involve gas mixtures. The other choices reflect different densities that would not accurately define air under standard conditions. Each incorrect choice represents a density that could either reflect different environmental conditions or other substances, which do not apply here.