A molecule of oxygen gas has chemical formula 02. If the temperature of oxygen gas in a container is 31C, find the root-mean-square speed for an oxygen molecule. 4. a. 393.3 m/s b. 486.8 m/s C. 533.4 m/s d. 502.2 m/s e. 490.6 m/s f. 422.1 m/s 16.00 Assist: With 2 oxygen atoms, the atomic mass of oxygen gas is 2 - 16.00 Then M = g/mol = kg/mol. Remember to convert the temperature from Celsius to Kelvin. Then use 3RT M (For a gas, the rms-speed is nearly the same as the average speed.)