The air constant, also known as the specific gas constant for dry air, is calculated using the universal gas constant (R) and the molar mass of dry air (Ma).
Here's the breakdown:
- Air Constant (Ra) = Universal Gas Constant (R) / Molar Mass of Dry Air (Ma)
Where:
- R (Universal Gas Constant): This is a fundamental physical constant that relates the energy scale in physics to temperature. Its value is approximately 8.314 J/(mol·K).
- Ma (Molar Mass of Dry Air): This is the average mass of one mole of dry air. It's approximately 0.0289645 kg/mol (or 28.9645 g/mol).
Therefore, the air constant (Ra) can be calculated as follows:
Ra = 8.314 J/(mol·K) / 0.0289645 kg/mol ≈ 287.058 J/(kg·K)
For practical purposes, the air constant (Ra) is often rounded to 287 J/(kg·K). This value is commonly used in thermodynamic calculations involving air.
Formula Summary:
- Ra = R / Ma
- Ra ≈ 287 J/(kg·K)
In summary, the air constant is derived by dividing the universal gas constant by the molar mass of dry air. The commonly used value is approximately 287 J/(kg·K).
