Kinetic Molecular Theory

Problem : Samples of H ₂ and He are at the same temperature. What is the ratio of their average velocities?

Solution for Problem 1 >>

The molar mass of H ₂ 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:

M H2 (V H2 )2 = M He(V He)2

Rearranging and solving this equation, we find that = .

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Problem : A volume of H ₂ and an identical volume of O ₂ are at the same temperature. Plot the Maxwell-Boltzmann speed distributions for the two gases on the same graph.

Solution for Problem 2 >>

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Problem : Calculate $v_{\mbox{rms}}$ for a sample of O ₂ at 300 K.

Solution for Problem 3 >>

v rms	=
	=
	=	480m/s

Remember that M must be in !

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Problem : Rank v _rms , , and v _p in order of increasing speed.

Solution for Problem 4 >>

v _p < < v _rms

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Problem : Calculate the ratio of the rates of effusion of H ₂ over He.

Solution for Problem 5 >>

	=
	=

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

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