Lowest Average Speed of Gases at 25C: H2S

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SUMMARY

The gas with the lowest average speed at 25°C is H2S, which has a molar mass of 34.08 g/mol. According to the formula for average speed, sqrt(3RT/M), gases with greater molar mass exhibit lower speeds. The kinetic energy (KE) of each molecule remains constant at the same temperature, as expressed by the equation KE = ½ m v² = 3/2 k_B T, where k_B is Boltzmann's constant. This confirms that H2S, having the highest molar mass among the options provided, indeed has the lowest average speed.

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Which of the following gases has the lowest average speed at 25C?
a.NH3
b.O2
c.H2S
d.CH4
Is it H2S? Given the formula sqrt(3RT/M), is it not true that the gas with the greatest molar mass will have the lowest speed?
NH3 = 17.03 g/mol
O2 = 32 g/mol
H2S = 34.08 g/mol
CH4 = 16.04 g/mol
Thanks.
 
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Yes, the KE of each molecule (at the same Temperature) is the same.
KE = ½ m v^2 = 3/2 k_B T
If you haven't seen it yet, k_B = k_Boltzmann = R/N_Avagadro
 

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