As we start learning about gas particles and how they 'behave' we learn that pressure, temperature, volume, and size (or mass) of particles will affect them. If you're given the masses of some common atmospheric gases and all of the gases are at the SAME temperature, rank the selected gases in the most logical order from fastest moving to slowest moving. The smaller the particle the faster it can move.

Question

hydrogen
water vapor
argon

Answer 1

To rank the selected gases (hydrogen, water vapor, and argon) in order of their average molecular speeds at the same temperature, we can refer to the concept that the average speed of gas particles is inversely related to the square root of their molar mass. This relation is expressed by the formula:

\[ v \propto \frac{1}{\sqrt{M}} \]

Where:

• \(v\) is the average speed of gas particles,
• \(M\) is the molar mass of the gas.

Now, let's look at the molar masses of the given gases:

1. Hydrogen (H₂): Molar mass ≈ 2 g/mol
2. Water vapor (H₂O): Molar mass ≈ 18 g/mol
3. Argon (Ar): Molar mass ≈ 40 g/mol

Now we can calculate their relative speeds:

• Hydrogen, with the lowest molar mass, will have the highest average speed.
• Water vapor, with a higher molar mass than hydrogen but lower than argon, will have a speed lower than hydrogen but higher than argon.
• Argon, with the highest molar mass, will have the lowest average speed.

Thus, the ranking of gases from fastest moving to slowest moving at the same temperature is:

1. Hydrogen (H₂)
2. Water vapor (H₂O)
3. Argon (Ar)

So, the final order is: Hydrogen > Water vapor > Argon.