Molecular Speeds: an Oxygen Molecule Falls in a Vacuum

Multiple Choice

Molecular speeds: An oxygen molecule falls in a vacuum. From what height must it fall so that its kinetic energy at the bottom equals the average energy of an oxygen molecule at 800 K? (The Boltzmann constant is 1.38 × 10^-23 J/K, the molecular weight of oxygen is 32.0 g/mol, and Avogadro's number is 6.022 × 10²³ molecules/mol.)

A) 31.8 km
B) 10.6 km
C) 21.1 km
D) 42.3 km