Topic 4

Question 1

What are the orders of J and K?

Answer 1

Photolysis rate J is unimolecular (1st order) whereas K is termolecular (2nd order).

Question 2

How are J and K linked to T and altitude?

Answer 2

J is independent of T but K is T dependent. J increases with altitude in general (due to photon flux) but K can increase/decrease at various altitudes.

Question 3

What is the proccess for determining a steady-state approximation?

Answer 3

To determine a steady-state approximation:
1. Set intermediate as d[I]/dt = 0
2. Any reactions that form the intermediate are postive wrt reactant(s) forming it. Any reaction constants using up intermediates are negative.
3. Set whole expression = 0.
4. Solve for [I] –> move all negative expressions containing intermediate (should all contain [I]) onto one side. On the other side have the fromation (photolysis) rate value.
5.Factor out conc [I]
6. Divide both sides by everything multiplied by [I].
End expression something like d[I]/dt = J1 / k1[O] + k2[M] ect = 0

Question 4

What is photon flux?

Answer 4

Photon flux is how many photons are available of a particular wavelength.

Question 5

What do the values of Quantum Yield for Dissociation mean?

Answer 5

A value of 1 for Quantum Yield of Dissocation means all photons observed will result in a dissociation. A value of 0 = no dissocation at all.

Question 6

Why does the Champan mechanism predict too much ozone?

Answer 6

The Chapman model preducts some 5 times too much O3 than observed because in reality, reactions with trace gases increases ozone destruction rate.

Question 7

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