Meteo 532 Atmospheric Chemistry

Problem set #3

assigned: 4 October, 2002

due: 11 October, 2002

1.  Termolecular reaction rate coefficients.
a. What is the reaction rate coefficients at 296 K and 960 hPa for the reactions:
i.) OH + NO₂ + M -> HNO₃ + M
ii.) H + O₂ + M -> HO₂ + M
iii.) CH₃ + O₂ + M -> CH₃O₂ + M
b. How much less than the low pressure limit values are the actual rate coefficients?


2. Consider the reaction:
CH₃O₂ + NO₂ + M <=> CH₃ O₂NO₂ + M
For T = 293 K, P = 960 hPa, what is the reverse reaction rate coefficient?

3.  Relaxation time for a simple reaction.

Consider the simple reaction system :      A + B -> C        k₁
                                                                 C -> A + B        k_-1

a.  What is the rate equation for [C]?
b.  At equilibrium, 0 = k₁[A]_eq[B]_eq  - k_-1 [C]_eq .  Suppose that [C] is displaced from equilibrium by an amount d [C], which by mass conservation will change both [A] and [B] by the same amount in the opposite direction.  Write down the rate equation for d [C].
c. Show that for a small d [C], the expression for d [C] is d [C] = d[C] _initialexp(-t/τ), where
    τ = {k_-1 + k₁([A]_eq + [B]_eq )}^-1 .