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.

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