chemistry definitions

Question 1

what is meant by air pollution?

Answer 1

it is the condition in which air contains high concentration of chemicals that may harm living things or damage non-living things

Question 2

what is the composition of air?

Answer 2

78% nitrogen
21% oxygen
1% other gases
- 0.03% carbon dioxide
- 0.97% noble gases (mainly argon)

Question 3

how is air separated? collecting oxygen/nitrogen

Answer 3

by the fractional distillation of liquified air
- they are first cooled and compressed, making molecules move closer
- this forms liquified air

Question 4

what is the source of carbon monoxide?

Answer 4

incomplete combustion of carbon containing compounds (petrol) in car engines

they are colourless and odourless, making it hard to be detected

Question 5

what is the effect of carbon monoxide?

Answer 5

it combined irreversibly with haemoglobin in blood, forming stable carboxyhaemoglobin, which prevents oxygenated blood from being transported to different part of the body, depriving them from oxygen

• causes breathing difficulties, fatigue, and death

Question 6

what can be used to reduce the carbon monoxide production?

Answer 6

catalytic converters converts carbon monoxide into less harmful gases such as carbon dioxide
(CO is oxidised)

2CO (g) + O2 (g) = 2CO2 (g)

Question 7

what is the source of nitrogen oxides?

Answer 7

• lightning activity where thermal energy is released, causing nitrogen and oxygen in the air to react together because of the high temperature
• nitrogen and oxygen in air combined to form carbon monoxide at high temperatures (in chemical factories/car engines)

nitrogen will react with oxygen to form nitrogen monoxide

nitrogen monoxide will react with oxygen to form nitrogen dioxide (brown in colour)

Question 8

what are the effects of nitrogen oxides?

Answer 8

-they can cause irritation to the eyes, lungs, and skin- high levels of oxides of nitrogen will result in the inflammation of lungs (bronchitis)

-forms petrochemical smog

• acid rain, where they react with water in the atmosphere to form nitric acid

4NO2 + O2 + 2H2O = 4HNO3

Question 9

how do we reduce the emission of oxides of nitrogen?

Answer 9

catalytic converters are used to remove oxides of nitrogen to form N2

Question 10

what is the source of sulfid dioxides?

Answer 10

combustion of fossil fuels such as coal and crude oil which contain sulfid as an impurity
- S + O2 = SO2

volcanic eruptions

Question 11

what are the effects of sulfur dioxide?

Answer 11

• acid rain
  • sulfur dioxide in the air will dissolve in water in the atmosphere, forming sulfurous acid
  • sulfurous acid will react will be oxidised to form sulfuric acid
• irritates eyes,lungs, causing breathing difficulties. high levels of SO2 will result in the inflammation of lungs (bronchitis)

Question 12

why is the pH level of unpolluted rainwater slightly below 7?

Answer 12

this is because carbon dioxide in the air will dissolve in water in the atmosphere, forming carbonic acid, which is a weak acid

Question 13

source of unburnt hydrocarbons?

Answer 13

hydrocarbons that have not been burnt in vehicle engines and are released in car exhaust fumes and chemical plants

Question 14

effects of unburnt hydrocarbons?

Answer 14

carcinogenic (causes cancer)

will react with oxides of nitrogen, forming ozone

Question 15

sources of methane

Answer 15

when plants or dead matter decay, also released from cows and other farm animals due to the digestion of food (from their farts)

decay of rubbish in landfills

Question 16

effects of methane

Answer 16

contributes to global warming because methane is a greenhouse gas

Question 17

sources of ozone

Answer 17

when nitrogen dioxide in the air reacts with unburnt hydrocarbons in the presence of SUNLIGHT

Question 18

effects of ozone

Answer 18

irritates eyes, lungs, throat, causing breathing difficulties

asthma inducing

produces petrochemical smog because sunlight acts on air and other pollutants

damages plant crops

Question 19

chemical equations in the catalytic converter

Answer 19

1. hot exhaust gases such as unburnt hydrocarbons, oxides of nitrogen and carbon monoxide are passed into catalytic converters that are fitted into car engines which are covered with platinum and rhodium catalysts

these harmful gases are converted into harmless compounds by redox reactions

• carbon monoxide is oxidised into carbon dioxide
  • 2CO + O2 = 2CO2
• carbon monoxide and nitrogen oxides will react in the presence of the platinum and rhodium catalysts where nitrogen monoxide is reduced to nitrogen and carbon dioxide
  • 2CO + 2NO = N2 + 2CO2
• unburnt hydrocarbons such as octane will be oxidised to form carbon dioxide, and water
  • 2C8H18 + 25O2 = 16CO2 + 18H2O

Question 20

how do we reduce air pollution my motor vehicles?

Answer 20

using cleaner fuels such as hydrogen, because when hydrogen burns, only water is produced

use electric cars, reducing exhaust gas emissions

Question 21

chemical equations in flue gas desulfurisation

Answer 21

1. as sulfur dioxide is being passed into the plant, it reacts with an aqueous suspension of calcium carbonate to form solid calcium sulfite and carbon dioxide gas

CaCO3 (s) + SO2 (g) = CaSO3 (s) + CO2 (g)

2 . calcium sulfite is further oxidised to form calcium sulfate (neutral)

2CaSO3 (s) + O2 (g) = 2CaSO4 (s)

Question 22

what are CFCs? chlorofluorocarbons

Answer 22

compounds that contain the elements carbon, fluorine, chlorine

Question 23

why is the ozone layer important?

Answer 23

absorbs UV radiation and blocks it from our skin to prevent skin cancer/ genetic mutations

Question 24

what is the carbon cycle?

Answer 24

it is a mechanism that maintains the level of carbon dioxide in the atmosphere

Question 25

what’s the main cause of the depletion of ozone layer?

Answer 25

CFCs

Question 26

which processes introduce CO2 into the atmosphere?

Answer 26

• respiration
• decomposition
• combustion of fuels

Question 27

equation for respiration

Answer 27

C6H12O6 (aq) + 6O2 (g) = 6H2O (l) + 6CO2 (g) + energy

Question 28

equation of combustion

Answer 28

CH4 + 2O2 = CO2 + 2H2O + heat energy

Question 29

how do we remove CO2 from the environment?

Answer 29

photosynthesis + PRESENCE IF SUNLIGHT AND CHLOROPHYLL

Question 30

equation for photosynthesis?

Answer 30

6H2O (l) + 6CO2 (g) = C6H12O6 (aq) + 6O2 (g)

Question 31

what is global warming

Answer 31

global warming is the increase in earths temperature due to the buildup of greenhouse gases in the atmosphere

Question 32

what are some examples of greenhouse gases

Answer 32

methane
CO2
water vapour

Question 33

why are greenhouse gases crucial?

Answer 33

it is crucial as it maintains a temperature that is suitable for sustaining life on earth

Question 34

what are the effects of too much greenhouse gases?

Answer 34

traps excess heat which results in the increasing in global temperatures

which then results in the increase in sea levels which leads to flood in low-lying countries and the melting of polar ice craps

more unusual weather conditions such as warm spells or droughts, unexpected hurricanes or floods

Question 35

define macromolecule

Answer 35

it is a large molecule formed from many small monomers joined together by covalent bonds

Question 36

addition polymerisation

Answer 36

when unsaturated monomers are joined together by the breaking of double bonds with no loss of atoms or molecules