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Problems

Problems

Problem : Samples of H2 and He are at the same temperature. What is the ratio of their average velocities?

The molar mass of H2 is half that of He. The temperatures of the two samples are the same, so their kinetic energies are the same. This leads to the following equation:

MH2(VH2)2 = MHe(VHe)2    

Rearranging and solving this equation, we find that = .

Problem : A volume of H2 and an identical volume of O2 are at the same temperature. Plot the Maxwell-Boltzmann speed distributions for the two gases on the same graph.

Problem : Calculate $v_{\mbox{rms}}$ for a sample of O2 at 300 K.


vrms=  
 =  
 =480m/s  

Remember that M must be in !

Problem : Rank vrms, , and vp in order of increasing speed.

vp < < vrms

Problem : Calculate the ratio of the rates of effusion of H2 over He.


=  
 =  

Note that this exactly mirrors the ratio of the average velocities of the two gases.