Sulfur In The Atmosphere

Question 1

Sulfur compounds in the atmosphere

Answer 1

Oxidised to SO2 and SO3

Question 2

Jung Layer

Answer 2

SO2 converted to H2SO4 giving Jung layer which is important for albedo of planet and is a global source of acid aerosol for perturbing stratospheric ozone chemistry

Question 3

Origins of acid rain

Answer 3

Gas phase oxidation of SO2 to H2SO4 then dissolution
Dissolution of SO2 then aqueous oxidation
Two mechanisms operate in parallel

Question 4

Gas phase oxidation/dissolution route of SO2 to H2SO4

Answer 4

Catalytic mechanism

Question 5

Dissolution/aqueous oxidation route of SO2 to H2SO4

Answer 5

Equilibrium dissolution of SO2 which is governed by Henry’s law then acts as a weak acid in solution

Question 6

Mechanism for redox reactions in atmospheric aerosol

Answer 6

D + A <-> [D…A] <-> [D+…A-] -> D+ + A-
Forms encounter pair then charge exchanged encounter pair
Key step is formation of encounter pair
Can do a SSA of this

Question 7

Diffusion-Limited Reaction

Answer 7

When rate constant for escape from the encounter pair is smaller than the rate constant for reaction k’diff < kr

Question 8

Activation-Limited Reaction

Answer 8

Rate constant for reaction in the encounter pair is larger than the rate constant for escape from it kr < k’diff

Question 9

Boundary conditions for redox reactions in atmospheric aerosol

Answer 9

In encounter pair [D] = 0
In bulk [D] = [D]

Question 10

Efficiency of tunnelling of electron from donor to acceptor depends on

Answer 10

RDA = width of electron transfer = separation of donor and acceptor
ΔEr = energy difference between donor HOMO and acceptor LUMO = reorganisation energy