At what temperature will the root-mean-square speed of oxygen molecules have the value of 640 m/s? 1 kilom has a mass of 32kg.

1 answer

You will find the formula you need at
http://chemistry.about.com/od/workedchemistryproblems/a/Calculate-Root-Mean-Square-Velocity-Of-Gas-Particles.htm
It is:

Vrms = sqrt(3RT/M)

M = 32*10^-3 kg/mol
R = ideal gas constant = 8.3145 (kg·m^2/sec^2)/K·mol

You were given the rms speed. Solve for T