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IGCSE Chemistry > 10. Chemistry Of The Enviroment > Flashcards

10. Chemistry Of The Enviroment Flashcards

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1
Q

Describe the composition of clean, dry air

A

78% Nitrogen
21% Oxygen
1% other variable gases (0.9% Argon, 0.04% CO2)

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2
Q

What are permanent gases + 2 Eg.s

A

Gases that cannot be liquefied by pressure alone at normal temperatures
Oxygen and nitrogen

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3
Q

What is fractional distillation used for in environmental chemistry

A

To separate oxygen from liquified air

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4
Q

What is fractional distillation used for

A

To separate oxygen from liquid air

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5
Q

Variable gases
Name 7 and what they do

A

Their concentration varies according to place and time
Argon (0.9%), CO2(0.04%), Nitrogen oxides, Helium, hydrogen, methane, neon

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6
Q

How gases are produced

A

Fractional distillation of air

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7
Q

What fractional is used for

A

P\producing gases by separating oxygen from liquid air

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8
Q

Industrial preparation of gases(3)

A

Pure air is liquified under high pressure and low temperatures (-200*)
Purified air contains nitrogen, argon and oxygen
Temperature is increased causing nitrogen to vapourise first, argon second and oxygen third

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9
Q

Use of gases gained from fractional distillation of air

A

Nitrogen- fertilizers
Argon - lightbulbs
Oxygen - makes steel for welding

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10
Q

Greenhouse effect

A

When some of the thermal energy from the sun is absorbed by greenhouse gases and is re-emitted in all directions reducing the amount of energy lost into space as it is trapped within the earths atmosphere causing global warming

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11
Q

Effect of greenhouse gases

A

Suns thermal energy enters earths atmosphere where some is reflected back from earths surface but most is absorbed and re-emmited back from earth into space.
Some of the thermal energy from the sun is absorbed by greenhouse gases and re-emitted in all directions. (Greenhoiuse effect)
This reduces the amount of energy lost into space and traps it within the earths atmosphere causing global temperature to rise(Global Warming)

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12
Q

Air pollutants(6)

A

Carbon dioxide
Particulates
Oxides of nitrogen
Sulfur oxides
Methane
Carbon monoxide

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13
Q

Source of sulfur dioxide

A

Combustion of fossil fuels containing sulfur (at power stations)

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14
Q

Sulfur dioxide - Adverse effects and solutions

A

Exposure cuases respiratory problems
Forms acid rain when dissolved in water-corrodes buildings + reduces productivity of soil+increases acidity of lakes

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15
Q

Sulfur dioxide - solution to adverse effects

A

Using low sulfur fules and flue gas desulfurisation

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16
Q

Flue gas desulfurisation

A

Calcium oxide being added to neutralise sulfur dioxide

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17
Q

Carbon dioxide source (formula as well)

A

Complete combustion of carbon containing fuels such as methane

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18
Q

Adverse effects of carbon dioxide

A

Higher levels of carbon dioxide lead to increased global warming which lead to climate change

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19
Q

Source of carbon monoxide

A

Incomplete combustion of carbon containing fuels such as there being limited oxygen when petrol is being burned in a car cylinder

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20
Q

Adverse effects of carbon monoxide

A

Toxic as it combines with haemoglobin in blood and prevents it from carrying oxygen

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21
Q

Strategies to rdiuce effects of carbon monoxide

A

Catalytic converters in cars prevent carbon monoxide from forming

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22
Q

Source of particulates

A

Incomplete combustion of carbon containing fuels (fossil fuels) can produce particulates of carbon (soot)
Incomplete combustion of methane can cause carbon monoxide and carbon

23
Q

Adverse effects of particulates

A

Respiratory problems and cancer

24
Q

Sources of oxides of nitrogen NO, NO2 (2)

A

Formed in car engine cylinders when oxygen and nitrogen from the air react at high temperatures and in the atmosphere during lightning storms

25
Q

Adverse effects of oxides of nitrogen

A

Repiratory problems - acute lung irritation and bronchitis
Gases form photochemical smog and acid rain when dissolved in water

26
Q

Strategies to reduce effect of nitrogen oxides (equation as well)

A

Catalytic converters in cars reduce the amount of nitrogen oxides in the air

2CO + 2NO → 2CO2 + N2

27
Q

Sources of methane (2)

A

Decomposition of vegetation
Waste gas from digestion in animals

28
Q

Adverse effects of methane

A

Increased global warming which leads to climate change

29
Q

How to reduce effects of climate change (4)

A

Planting trees
Reduction in lifestock farming
Decreasing the use of fossil fuels
Increasing the use of hydrogen and renewable energy such as wind and solar

30
Q

How to reduce effects of acid rain (2)

A

Reducing emmisions of sulfur dioxide by using low sulfur fuels and flue desulfurisation with calcium oxide
Use of catalytic converters in vehichles

31
Q

Catalysts used in catalytic converters and what they do

A

Platinum-rhodium alloy which removes pollutant gases from the exhaust by oxidising them and reducing them at 200*c

32
Q

Equation for what happens to carbon monoxide and nitrogegn monoxide in a catalytic converter

A

CO is oxidied, NO is reduced
2NO + CO2 -> 2CO2 + N2

33
Q

What happens to and equation for carbon monoxide in a catalytic converter

A

It is oxidised
2CO + O2 -> 2CO2

34
Q

What happens to and equation for hydrocarbons in a catalytic converter

A

They are oxidised
C7H16 + 11O2 -> 7CO2 + 8H2O

35
Q

Photosynthesis definition, word equation and symbol equation

A

Reaction between CO2 and H2O to produce oxygen and glucose in the presence of chlorophyl using energy from light
Carbon dioxide + water -> glucose + oxygen
6CO2 + 6H20 -> C6H12O6 + 6O2

36
Q

Substances used for Chemical test for water

A

Copper(II) sulphate (CuSO4)
Cobalt(II) chloride paper (CoCl2)

37
Q

Chemical test for water using anhydrous copper (II) sulphate

A

It is a reversible reaction, CuSO4 + H2O -> CuSO4.5H20
Colour change is due to the crystallisation of water as the water bonds to the copper atoms
Reaction from off-white to blue is exothermic

38
Q

Chemical test for water using cobalt (II) chloride paper (CoCl2)

A

Turns from blue to pink in the presence of water
Hydrous copper chloride is formed
Forward reaction is exothermic as it requires bonds to form

39
Q

Tests for pure water

A

Pure substances boil at specific, sharp temperatures. Pure water boils at 100ºC.
Impurities tend to increase the boiling point, so water that boils above 100ºC is impure
Impurities tend to decrease the melting point. Water that melts below 100ºC is impure

40
Q

Distilled water

A

Water that has been heated to form a vapour and then condensed back to a liquid so that it contains very few impurities
Used in practical chemistry because of its hugh purity

41
Q

Natural sources of water(3)

A

Lakes
Rivers
Underground water sources

42
Q

3 ways water is used + examples of each

A

Home - drinking, cooking, cleaning, as a solvent, drinking
Agriculture - water for crops, drinking for animals
Industrial - solvent, hydroelectric power manufacture of chemicals

43
Q

Beneficial substances found in water from natural sources(2)

A

Dissolved oxygen - for aquatic life
Metal compounds - provides essential minerals for life

44
Q

Harmful substances in water from natural sources (4)

A

Metal compounds - toxic
Plastics - harm aquatic life
Nitrates + phosphates from fertilizers - lead to deoxigination of water and damage aquatic life
Sewage- contain harmful microbes which cause disease

45
Q

Process of water treatment (11)

A

Water is pumped from source to reservoir
Water is aerated to separate iron compounds
Aluminium sulphate (Al2(SO4)3) is added to coagulate colloidal clay
Water is fed into sedimentation tank
Water passes through sand beds under pressure
Chlorine added to clear bacteria and algae (germicidal action)
Sulfur dioxide is added to remove excess chlorine
Water is neutralised using a lime slurry
Water is filtered through granulated activated carbon which improves the taste and smell by removing dissolved gasses
Fluoride added to prevent tooth decay
Water pumped to users

46
Q

Germicidal action

A

Hydrochlorous acid penetrating cell walls by destroying the lipids and the internal structure

47
Q

Commonly used as fertilizers

A

Ammonium salts and nitrates

48
Q

What fertilizers contain and what they each promote

A

Nitrogen - makes chlorophyl and protein which promotes healthy leaves
Phosphorus - promotes healthy roots
Potassium - promotes growth and healthy fruit and flowers

49
Q

What water soluble ions fertiliser compounds contain/sources

A

Ammonium ions (NH4+) and nitrate ions (NO3-) - source of soluble nitrate
Phosphate ions (PO4 -3) - source of soluble phosphorus
Most common potassium compounds dissolve in water to produce potassium ions (K+)

50
Q

3 common fertilizer compounds

A

Ammonium nitrate (NH4NO3)
Ammonium phosphate ((NH4)3PO4)
Potassium sulphate (K2SO4)

51
Q

How do you know which fertilizer would be most effective

A

The one with the most elements from nitrogen, phosphorus and pottassium

52
Q

Use of sedimentation

A

To remove soluble solids

53
Q

Why we use distilled water in a chemical lab instead of tap water

A

Because it contained fewer chemical impurities

54
Q

How to test for purity of water

A

Freeze it then see if it melts at 0 degrees, and see if it boils at 100 degrees

IGCSE Chemistry (21 decks)

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