Hi there, I'm looking to find the most probable speed of atoms ejected from an oven. Temp (T) is 900°C (so 1173.15K). The material is aluminium with molar mass 0.027kg mol^{-1} I've got the formula v_{mp}=√(2kT/m) I'm fine with everything above, but I'm not sure what value to use as the Boltzmann constant k. Can anyone please help me here? Do I have the right equation and what value for the constant should I use (sounds silly, but it changes depending upon units. I've tried a couple but get silly tiny speeds out. I think I should expect something in the region of a few hundred metres per second). Many thanks Bob
In SI units: K = 1.38e-23 J/K m = mass of one molecule = 0.027/6.022e23 kg T = 1173 K ... which gives a velocity of "hundreds of m/s" as you expected.