Speed of gases at the same temperature

Question

Which one of the following gases would be expected to have the highest speed if all the gases were at the same temperature?

A) O2

B) N2

C) F2

D) H2

Answer 1

Remember that T = E_k,avg = (1/2) m v_rms²

With T constant mv² = const,, v² = const/m, v=const/sqrt(m)

Simply, as m goes up, v goes down and vice versa. It's actually more quantitative: If the M is tripled, the velocity of the heavier gas will be 1/sqrt(3) as fast.

There is also the formula for the v_rms = sqrt (3RT/M_i) which shows that v goes up as T goes up and down as M_i goes up.

Here lightest gas is fastest.

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