According to this answer, the partial pressure of a gas decreases exponentially in height, when placed in gravity. For a mixture of gases, the partial pressures of each component follows this law individually. So, when you add all the partial pressures up to get the total pressure, I would expect to get a sum of exponentials, which is not an exponential itself. Does this mean that the total pressure of a mixture of gases does not follow an exponential decay?
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asked Sep 27, 2022 at 10:26
AccidentalTaylorExpansionAccidentalTaylorExpansion
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2$\begingroup$ @AslanMonahov Please do not use comments to answer posts - this is very strongly discouraged. Also note that you can gain much more reputation points from posting an answer than a comment. $\endgroup$– StephenG - Help UkraineCommented Sep 27, 2022 at 10:58
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2$\begingroup$ Also, in the atmosphere, there is dis;persional/convective mixing all the way down to very fine scales, so, aside from the effects of chemical reactions, the separation that occurs in an undisturbed column does not occur in the atmosphere. $\endgroup$– Chet MillerCommented Sep 27, 2022 at 10:59
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$\begingroup$ Temperature vertical profile would break a clean exponential even for a pure ideal gas and homogeneous gravity. $\endgroup$– PoutnikCommented Sep 27, 2022 at 16:57
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1 Answer
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Yes; the sum of exponential functions with different coefficients is not an exponential function but in this case looks approximately like an exponential function, considering that most of the atmosphere consists of oxygen and nitrogen with similar masses.
