Acid gases in the atmosphere

Question 1

Examples of natural acid gases

Answer 1

SO2, H2S, OCS, CS2, DMS, DMDS

Question 2

Origin of the gases produced

Answer 2

Volcanoes: SO2, H2S, OCS
Vegetation/Soils: H2S, OCS, CS2, DMS and DMDS
Oceans: H2S, OCS, CS2, DMS

Question 3

What is DMS

Answer 3

Dimethyl sulfide

Question 4

What is DMDS

Answer 4

Dimethyl (Di)sulfide

Question 5

Chemical reactions of sulphur species (Sulphur Species Oxidation - H2S)

Answer 5

OH + H2S -> SH + H2O
SH + O3 -> HSO + O2
HSO + O3 -> HSO2 + O2
HSO2 + O2 -> SO2 + HO2
HO2 + NO -> OH (reformation) + NO2

Question 6

Chemical reactions of sulphur species (3 x Sulphur Species Oxidations - SO2)

Answer 6

1. Gas Phase Oxidation -> Dissolution
2. Dissolution -> Aqueous Oxidation
3. SO2(g) -> H2SO4 (g) -> H2SO4 (aq)
4. SO2(g) -> H2SO3 (aq) -> H2SO4 (aq)
5. OH with SO2

OH + SO2 -> HSO3 (M third body - above arrow)

HSO3 + O2 -> SO3 (used in *) + HO2 (used in **)

• SO3 (g) -> H2SO4 (aq) via H2O aerosol

** HO2 + NO -> OH (reform) + NO2

Question 7

Determining pH of given CO2 concentration: Working out concentration of CO2 and pressure of CO2 (3 equations)

SEE LECTURE NOTES

Answer 7

Conc of CO2:

[CO2(aq)] = K(H2CO2)p(CO2)

Pressure of CO2:

p(CO2) = (p(o) - p(H2O))x(CO2)

pH = -log(H+)

Then finally pH = ***

Question 8

Compare and contrast ways to produce soda ash (Leblanc/Solvay)

Answer 8

Leblanc vs Solvay

Leblanc: Wide spread acid due to byproducts (HCl (cleared with HCl scrubber), H2SO4, NO (goes onto produce HNO3), Soot and CO2)

Solvay: recycles CO2 and NH3

Question 9

What are the effects of acid precipitates

Answer 9

1. Damages Buildings
2. Environment
3. Over fertilisation with NO3- (eutrophication)
4. Acid leaching (toxic heavy metals) from soils into rivers and water courses

Question 10

What are the measures in controlling the acid precipitates

Answer 10

1. Adding ammonia water (ammonium hydroxide)
2. Adding slaked lime (calcium hydroxide) to lakes
3. Adding calcium carbonate to soil
4. Flue gas desulfurisation to reduce SOx emissions

Question 11

What are other power sources?

Answer 11

Gas-powered stations 
Shale gas (gas from fracking)
Methane clathrates (methane trapped in crystal structure of water)