consider 3 identical flasks filled with different gases Consider three identical

Question

consider 3 identical flasks filled with different gases Consider three identical flasks filled with different gases: CO at 750 torr and 0 degree C N_2 at 250 torr and 0 degree C H_2 at 500 torr and 0 degree C In which flask will the molecules have the greatest average kinetic energy? In which flask will the molecules have the greatest U_rms? In which flask will the molecules have the smallest U_rms? Which flask will have the largest number of molecules? Rank the flasks in term of increasing gas density

Explanation / Answer

This is kinetic theory of gases.

a)

As the temperatures are same, kinetic energy is also same.

Therefore, answer to first question is All the flasks have same kinetic energy.

(b)

rms = (3RT/M)½

Less the mass greatest the µrms.

Flask 3 (the gas with the lightest molecular mass moves fastest if KE is the same for all                                     samples)

c)

Flask 1 (the gas with the highest molecular mass moves slowest as KE is the same for all                                  samples)

d)

Here we have pressure of gases.

To calculate the number of molecules.

Number of molecules = Pressure/molar mass * Avogadro number

Molar mass of CO = 28.01g/mol

Molar mass of N2 = 28.00 g/mol

Molar mass of H2 = 2.015 g/mol

CO = 750/28.01 * 6.022 x 1023 = 1.612 * 10^25

N2 = 250/28 * 6.022 x 1023= 5.37 * 10^24

H2 = 500/2.015 * 6.022 x 1023= 1.49 * 10^26

Hydrogen has the largest number of molecules.

e)

Increasing gas density

Density = P.M / RT

But as R and T are constant. Gas density depends on Pressure * Molar mass

Flask 1 = 750 * 28.01 = 21007.8

Flask 2 = 250 * 28.00 = 7000

Flask 3 = 500 * 2.015 = 1007.5

Flask 3 < Flask 2 < Flask 1

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