The helium and argon are put in the flask at the same room temperature (300 K). The ratio of average kinetic energies (per molecule) of helium and argon is: (Given: Molar mass of helium = 4 g/mol, Molar mass of argon = 40 g/mol)
- 1 : 10
- 10 : 1
- 1 : 10
- 1 : 1
Answer
(4) 1 : 1
Solution
Average kinetic energy per molecule of a gas: KE = 32kBT
It depends only on the absolute temperature, not on the molar mass.
(Helium and argon are both monatomic, so even their total kinetic energies per molecule are 32kBT.)
T is the same (300 K) for both gases,
KEHe : KEAr = 1 : 1
(The molar masses affect only the speeds: vrms 1 M.)
Answer: (4)