Answer: Helium has a higher rms speed (lower molar mass) so it diffuses out faster.
- A Helium atoms are actually heavier than the nitrogen and oxygen in air
- B Helium has a higher rms speed (lower molar mass) so it diffuses out faster
- C Helium chemically reacts with and weakens the balloon material
- D The enclosed air has a lower internal pressure than the helium
Correct answer: B. Helium has a higher rms speed (lower molar mass) so it diffuses out faster
Explanation: Since v<sub>rms</sub> ∝ 1/√M, lighter helium molecules move faster than air molecules at the same temperature, leading to faster effusion/diffusion through small pores.
Not all gas molecules move at the same speed - the Maxwell-Boltzmann distribution shows the spread, with the most probable speed vp slightly less than the average vavg, which is slightly less than the root-mean-square speed vrms used in the pressure formula.
Concept context
Kinetic theory of gases connects molecular motion to pressure and temperature, explaining gas laws, specific heats, and molecular speeds.