Question

Compute the root-mean-square speed of He molecules in a sample of helium gas at a temperature of 168°C.

Compute the root-mean-square speed of N₂ molecules in a sample of nitrogen gas at a temperature of 28°C.

Arrange the following molecules in order of increasing average molecular speed. All are at the same temperature.

methane, argon, sulfur dioxide, neon

Enter formulas in the boxes below: 1 = slowest, 4 = fastest

Arrange the following molecules in order of increasing average molecular speed.

O₃ at 330K, CH₄ at 466K, O₃ at 369K, O₂ at 369K

Enter formulas and temperatures in the boxes below:
1 = slowest, 4 = fastest

Answer 1

Root mean square speed,

where,

R = gas constant = 8.314 J/mol.K

T = temperature

M = molar mass

For He,

M = 0.004 kg/mol

T = 168 ^oC = (168 + 273.15) K = 441.15 K

Thus, for He,

           = 1659 m/s

-

For N₂,

M = 0.028 kg/mol

T = 28 ^oC = (28 + 273.15) K = 301.15 K

Thus, for N₂,

           = 518 m/s