Calculate the root mean square velocity of the following gases at 25°C.

Question

Calculate the root mean square velocity of the following gases at 25°C.

a. He

b. Ar

Answer 1

I find the equation for root mean square velocity u from u² = 3RT/MM where R in this case is 8.314 x 10³ g m²/ s² mol K and MM is Molar Mass.

a) For He, u² = 3 (8.314 x 10³) (25 + 273K) / 4.003 = 1.858 x 10⁶ which yields u = 1,363 m/s.

b) For Ar, u² = 3 (8.314 x 10³) (25 + 273K) / 39.95 = 1.861 x 10⁶ which yields u = 431 m/s.