Question

Two sealed gas tanks of equal volume are separately filled with H2 and N2 gases, each at 20oC and 1.00 atm. For each answer to the following questions, please provide explanations.

(a) Which gas has the greater average molecular kinetic energy?
(b) Which gas has the greater average molecular speed?
(c) Which gas has the greater average frequency of collisions with the container? (d) Which tank contains more molecules?

Answer 1

a)

All gases are at T = 20°C, so they all have the SAME average kinetic anergy

since T is a measure of AVERAGE kinetic energy, expect the SAME vlaue for H2 and N2

b)

greater average molecular speed-->

since the Energy associated to T = 20°C is the SAME for H2 and N2

then

E = 1/2*m*v^2

note that E is constant for both

so, only "m" changes, therefore, V increases to the 2nd power...

for light material, such as H2, expect the largest Velocity

c)

Since H2 is faster, expect much more collisions between H2 molecules than N2

d)

The gas with most molecules will be NONE

since this has nothing to do with "mass" rather with "moles" and moles of gases is the same

PV = nRT

for both cases, n is the same value