Acid deposition

Question 1

2 main causes of acid rain

Answer 1

SOx and NOx dissolving in water in the atmosphere to form HNO3, H2SO4, HNO2, H2SO3

Question 2

sulphurous acid formation

Answer 2

• Often SO2 in atmosphere comes from volcanoes. Anthropogenic emissions -> smelting of sulfide ores/ combustion of fuels containing sulphur

S(g) + O2(g) –> SO2(g)
SO2(g) + H2O(l) –> H2SO3(aq)

Question 3

Sulphuric acid formation

Answer 3

• In presence of UV light + catalysed by particulates in the atmosphere –> sulphuric dioxide converted to sulphuric trioxide

2SO2 + O2 –> 2SO3

• SO3 reacts w water to form sulphuric acid

SO3 + H2O –> H2SO4

Question 4

Nitrous oxides

Answer 4

N2 + O2 –> 2NO (often in car engines where combustion at high temps occurs)
4NO + 2H2O + O2 –> 4HNO2 (REACTS WITH WATER IN THE PRESENCE OF OXYGEN)

2NO + O2 –> 2NO2 (mainly no is oxidised in the atmosphere to form no2)
2NO2 + H2O –> HNO3 + HNO2 (nO2 MAY REACT DIRECTLY WITH water to form a mix of these two acids)
4NO2 + O2 + 2H2O –> 4HNO3

Question 5

Acid deposition

Answer 5

The process by which acidic particles, gases and precipitation leave the atmosphere

Question 6

wet v dry deposition

Answer 6

wet - when acific oxides get dissolved in and react with the water in the air
dry - when gases and dust get acidic

Question 7

Marble/limestone reaction with water

Answer 7

CaCO3 + H2SO4 –> CO2 + CaSO4 + H2O

CO3^(2-) + 2H^(+) –> H2O + CO2

Question 8

Removing sulphur from fuels (pre-combustion)

Answer 8

• Switching to fuels without sulphur
• Increasing car sharing, PT use to reduce combustion of sulphur-containing fuels
• Removing sulphur from fuels (coal –> crushing and then flotation, hydrodesulphurisation for oil)

Question 9

Removing sulphur from fuels (post-combustion)

Answer 9

• Flue gas desulphurisation
• shooting a wet slurry of lime (CaO) at the flue gas so it reacts with the sulphur oxides to form calcium sulfite(s) which is removed as a solid