At a mountain top the air is thinner than at sea level.
Statement I: The fraction of helium relative to nitrogen in the air is larger on the mountain top than at sea level.
Statement II: The concentration of a gas falls with height as $e^{- \frac{M g h}{RT}}$ , so a lighter gas falls off more slowly.

Question

At a mountain top the air is thinner than at sea level.

Statement I: The fraction of helium relative to nitrogen in the air is larger on the mountain top than at sea level.

Statement II: The concentration of a gas falls with height as $e^{- \frac{M g h}{RT}}$ , so a lighter gas falls off more slowly.

TestHub · Accepted Answer

Helium (M = 4) has a much larger scale height than nitrogen (M = 28), so it is less depleted with height. Both statements are true. A.

Physics - Heat & Thermo Question with Solution | TestHub