Question

The escape velocity required for gas molecules to overcome the earth’s gravity and go off to outer space is 1.12 x 103m/s at 15oC. Calculate the molar mass of a species with that velocity.

Answer 1

Here we use the root-mean-square velocity:
V(rms)² = (3RT)/M; where R is the molar gas constant, T is the temperature in Kelvin and M is the molar mass.
(1.12 x 10³)² = (3 x 8.314 x (273 + 15))/M
M = 5.72 x 10⁻³ kg = 5.72 grams