What is the approximate mole fraction of neon (Ne) in dry air at sea level?

• A. 0.000018
• B. 0.0093
• C. 0.00039
• D. 0.21

Answer: (A)

Verified step by step guidance

1. Understand that mole fraction is defined as the ratio of the number of moles of a component to the total number of moles in the mixture. Mathematically, mole fraction of neon, \(X_{Ne} = \frac{n_{Ne}}{n_{total}}\).
2. Recognize that dry air is a mixture of gases, primarily nitrogen (N\(_2\)), oxygen (O\(_2\)), argon (Ar), carbon dioxide (CO\(_2\)), neon (Ne), and others, each with a known approximate volume or mole percentage at sea level.
3. Find the typical mole percentage or volume percentage of neon in dry air at sea level from standard atmospheric composition data. Neon is a trace gas, usually around 0.0018% by volume.
4. Convert the volume percentage of neon to mole fraction by dividing the percentage by 100, since for ideal gases at the same conditions, volume percentage equals mole percentage.
5. Express the mole fraction of neon as \(X_{Ne} = \frac{0.0018}{100} = 0.000018\), which is the approximate mole fraction of neon in dry air at sea level.