DF10

Question 1

What is a primary pollutant?

Answer 1

An air pollutant emitted directly from a source.

Question 2

What are secondary pollutants?

Answer 2

When primary pollutants react in the atmosphere.

Question 3

What are some of the primary pollutants (from vehicles and other sources)?

Answer 3

• particulates
• volatile organic compounds (VOC)
• carbon monoxide (CO)
• carbon dioxide (CO2)
• nitrogen oxides (NOx)
• sulfur oxides (SOx)

Question 4

What are particulates?

Answer 4

Particularly small carbon particles smaller than 2.5 x 10^-12 m.

Question 5

What are the major sources of particulates?

Answer 5

• volcanoes
• burning fuels
• burning coal

Question 6

What are the major polluting effects of particulates?

Answer 6

Penetrate deep into the human body - causing heart attacks and lung cancer.

Question 7

What are the major sources of VOC?

Answer 7

• plants

- unburnt fuel from petrol engines

Question 8

What are the major polluting effects of VOC?

Answer 8

photochemical smog

Question 9

What are the major sources of CO?

Answer 9

• incomplete combustion of hydrocarbons in fossil fuels

- burning biomass

Question 10

What are the major polluting effects of CO?

Answer 10

• toxic gas

- photochemical smog

Question 11

What are the major sources of CO2?

Answer 11

combustion of fossil fuels

Question 12

What are the major polluting effects of CO2?

Answer 12

greenhouse effect

Question 13

What are the major sources of NOx?

Answer 13

combustion of fuels in power stations and vehicles

Question 14

What are the major polluting effects of NOx?

Answer 14

• acid rain

- photochemical smog

Question 15

What are the major sources of SOx?

Answer 15

• volcanoes

- burning of fuels containing sulfur

Question 16

What are the major polluting effects of SOx?

Answer 16

• toxic gas

- acid rain

Question 17

What is the equation for complete combustion?

Answer 17

hydrocarbon/alcohol + oxygen → carbon dioxide + water

Question 18

What is the equation for incomplete combustion?

Answer 18

hydrocarbon/alcohol + oxygen → CO + C + water

Question 19

Why does incomplete combustion occur?

Answer 19

Limited supply of oxygen - either CO or C produced (and water).

Question 20

How is SO2 produced from fuels?

Answer 20

Burning of sulfur compounds in fuels:

S + O2 → SO2

Question 21

How are NOx produced from fuels?

Answer 21

Burning of nitrogen compounds in fuels:

N2 + O2 → 2NO

Question 22

How are NOx produced from vehicles?

Answer 22

• burning in fuels

- nitrogen and oxygen in the air react in very high temperatures of a vehicle engine

Question 23

How is acid rain produced from SOx?

Answer 23

• SO2 + H2O → H2SO3 (atmosphere)
• then SO2 is oxidised to make SO3 in stratosphere
• SO3 + H2O → H2SO4

Question 24

How is acid rain produced from NOx?

Answer 24

2NO/2NO2 + H2O + 1.5O2 → 2HNO3 (atmosphere)

Question 25

What are the harmful effects of acid rain?

Answer 25

- breathing difficulties - corrodes limestone buildings - kills forests - kills life in lakes

Question 26

How is photochemical smog produced?

Answer 26

When primary pollutants absorb sunlight to produce secondary pollutants (e.g. ozone, NO2, nitric acid).

Question 27

What are the harmful effects of photochemical smog?

Answer 27

- haziness - reduced visibility in air - respiratory problems in humans

Question 28

How are pollutants removed in petrol engines?

Answer 28

CO: 2CO + O2 → 2CO2 hydrocarbons: complete combustion NO: 2NO + CO → N2 + 2CO2

Question 29

Where do the reactions to remove pollutants in petrol engines occur?

Answer 29

In a three-way catalytic converter - consisting of platinum/rhodium (on a porous support).

Question 30

How are SOx pollutants best prevented?

Answer 30

Removing sulfur impurities from fuels.

Question 31

What are the main pollutants present in diesel engines?

Answer 31

- CO - hydrocarbons - particulates - NOx compounds

Question 32

How are CO and hydrocarbons removed in diesel engines?

Answer 32

CO: 2CO + O2 → 2CO2 hydrocarbons: complete combustion

Question 33

How are particulates removed in diesel engines?

Answer 33

- diesel particulate filters | - regeneration (burning it off)

Question 34

How are NOx compounds removed in diesel engines?

Answer 34

- Recycle some of the exhaust gases through the cylinder, lowering the temperature and amount of NOx formed. - Reagent (e.g. ammonia) is used rather than a catalyst

Question 35

How are is SO2 best prevented?

Answer 35

Using ultra low-sulfur fuels