Acid rain

Question 1

acid rain

Answer 1

acid rain is rain that is more acidic than normal (<5 pH)

rainwater is naturally slightly acidic, 6-7 pH

Question 2

sulfur dioxide in fuels

Answer 2

hydrocarbon fuels may contain impurities such as sulfur compounds

fuels are burnt in power stations and vehicles

when the fuels burn, the sulfur is oxidised to form sulfur dioxide

sulfur + oxygen -> sulfur dioxide
S(s) + O2(g) -> SO2

Question 3

sulfur dioxide and forming acid rain

Answer 3

non-metal oxide
dissolves in rainwater to form an acidic solution

-SO2 + H2O -> H2SO3
forms sulfurous acid

-H2SO3 + O2 -> 2H2SO4
sulfurous acid reacts with oxygen in the atmosphere and becomes sulfuric acid

acid rain is a mixture of diluted sulfurous and sulfuric acid

Question 4

effects of acid rain on plants/animals

Answer 4

soil becomes more/too acidic

• crops don’t grow because of the pH
• plants can’t absorb nutrients in the soil
• organisms in soil are harmed

rivers and lakes become too acidic

• kills fish and insects (because of pH)
• prevents fish eggs from hatching

trees are damaged
-directly from the rain and also from the soil being acidic

Question 5

effects of acid rain on buildings

Answer 5

acid breaks the structure of limestone/marble
-causes weathering/erosion of buildings

-calcium carbonate + sulfuric acid -> calcium sulfate + water + carbon dioxide

reacts with metals
-increasing rate of corrosion (weakens them)

-iron + sulfuric acid -> iron (III) sulfate + hydrogen

Question 6

reducing environmental damage

Answer 6

• removing sulfur from petrol, diesel, fuel oil at refinery before selling
• flue gas defulfurisation to prevent sulfur dioxide leaving power station chimneys
• adding calcium carbonate or calcium hydroxide to fields and lakes to neutralise excess acid from acid rain
• catalytic converters in internal combustion engines remove most NOx gases

Question 7

formation of nitrogen oxides

Answer 7

internal combustion engines:

• (diesel) car engines
• fuel mixes with air and ignites (mini explosions)
• temperature reaches high enough levels to allow nitrogen and oxygen in the air to react together
• forms oxides of nitrogen

Question 8

nitrogen oxides, acid rain and other environmental problems

Answer 8

• NOx forms nitric acid when it reacts with moisture in the air
• forms acid rain
• oxides of nitrogen also cause respiratory disease/bronchitis
• reacts with pollutants when in sunlight to create photochemical smog

Question 9

photochemical smog

Answer 9

mixture of fog, oxides of nitrogen, and sunlight

Question 10

Oxides of nitrogen, NOx, are atmospheric pollutants. They may contribute to acid rain.

a) Explain why oxides of nitrogen are produced when hydrocarbon fuels are used in vehicle and aircraft engines

b) Balance the equation to represent the production of nitrogen dioxide:
N2(g) + O2(g) -> NO2(g)

Answer 10

a) air goes into the engine so the fuel can burn

N2 and O2 from the air react together at the high temperatures in the engines to produce oxides of nitrogen

b) N2 + 2O2 -> 2NO2

Question 11

State two environmental problems caused by acid rain

Answer 11

• weathering of buildings/statues
• damage to trees
• harm to living things in river/lakes/soil

Question 12

Explain why, when hydrocarbon fuels are used:

a) sulfur dioxide is produced
b) oxides of nitrogen are produced

Answer 12

a) hydrocarbon fuels contain impurities of sulfur compounds
sulfur is oxidised to sulfur dioxide when the fuel is used

b) nitrogen and oxygen from the air react together in the high temperatures inside an engine