The effective atomic mass of air refers to the average atomic mass of all the elements present in the Earth's atmosphere. Air is composed primarily of nitrogen (N2) and oxygen (O2), along with trace amounts of other gases such as argon, carbon dioxide, neon, helium, and various pollutants.
To calculate the effective atomic mass of air, we need to consider the relative abundances of the different gases present. Here are the approximate average atomic masses and abundances (by volume) of the major components of air:
- Nitrogen (N2): Average atomic mass = 28.0134 u (0.7808 volume fraction)
- Oxygen (O2): Average atomic mass = 31.9988 u (0.2095 volume fraction)
- Argon (Ar): Average atomic mass = 39.948 u (0.0093 volume fraction)
The other trace gases and pollutants have relatively negligible contributions to the overall average atomic mass of air, so for simplicity, we will not consider them in this calculation.
To find the effective atomic mass of air, we can multiply the atomic mass of each component by its volume fraction (or molar fraction) and sum them up:
Effective Atomic Mass of Air = (Atomic Mass of N2 × Volume Fraction of N2) + (Atomic Mass of O2 × Volume Fraction of O2) + (Atomic Mass of Ar × Volume Fraction of Ar)
Plugging in the values:
Effective Atomic Mass of Air = (28.0134 u × 0.7808) + (31.9988 u × 0.2095) + (39.948 u × 0.0093)
Calculating this expression gives us the approximate effective atomic mass of air:
Effective Atomic Mass of Air ≈ 28.97 u
Please note that this value is an approximation, and the actual composition of air can vary slightly based on location and atmospheric conditions.