How Do Atmospheric Conditions at the Stratopause Compare to Sea Level?

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SUMMARY

The discussion focuses on calculating atmospheric pressure and gas concentrations at the stratopause, as well as determining the reaction rate for a specific chemical reaction involving hydroxyl and hydrogen. The atmospheric pressure at the stratopause is significantly lower than at sea level, with dioxygen and dinitrogen concentrations also reduced. The Arrhenius parameters provided for the reaction, with A = 8 x 10^10 s-1 and Ea = 42 kJ mol-1, are essential for calculating the reaction rate, which is influenced by the concentration of hydroxyl at 7 x 105 molecules cm-3 and hydrogen at 530 ppbv.

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  • Understanding of atmospheric pressure calculations
  • Knowledge of gas concentration units (mol m-3, ppbv)
  • Familiarity with the Arrhenius equation and its parameters
  • Basic principles of chemical kinetics
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Hi,

I am studying for a midterm and I need help on 2 practice questions from the textbook which I have no idea how to start.

The first one is:
Calculate the atmospheric pressure at the stratopause. What are the concentrations (mol m-3) of dioxygen and dinitrogen at this altitude? How do these concentrations compare with the corresponding values at sea level?

I have no idea how I am able to start this question. Any tips would be greatly appreciated.

The second one is:
At a particular temperature, the Arrhenius parameters for the reaction:

•OH + H2 → H2O + •H

Are A = 8 x 10^10 s -1, and Ea = 42 kJ mol-1. Given that the concentration of hydroxyl in the atmosphere is 7 x 10^5 molecules cm-3 and that of H2 is 530 ppbv, calculate the rate of reaction (units of molecule cm-3 s-1) for this process.

I have tried this question with other formulas but it just always ends up with a very very large number. Any tips would be greatly appreciated.

Thank You.
 
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