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Chemistry - IGCSE > Ch 17 - (Chemistry of our environment) > Flashcards

Ch 17 - (Chemistry of our environment) Flashcards

1
Q

What is used to test for water?

A
  • Cobalt (II) chloride
  • Copper (II) sulfate
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2
Q

How is the test for cobalt chloride done?

A

using cobalt chloride paper

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3
Q

what is the word equation for cobalt (II) chloride?

A

Anhydrous cobalt (II) chloride + water –> <– hydrated cobalt (II) chloride

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4
Q

what is the symbol equation for cobalt (II) chloride?

A

CoCl2 (s) + 6H2O (l) –> <– CoCl2.6H2O (s)

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5
Q

what is the word equation for copper (II) sulfate?

A

Anhydrous copper (II) sulfate + water –> <– hydrated copper (II) sulfate

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6
Q

what is the symbol equation for copper (II) sulfate?

A

CuSO4 (s) + 6H2O (l) –> <– CuSO4.5H2O (s)

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7
Q

What is the positive test for water in copper sulfate and cobalt chlroide?

A

cobalt (II) chlroide: Blue to pink

Copper (II) sulfate: White to blue

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8
Q

What can be used to test for the purity of a substance?

A

Melting point and boiling point

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9
Q

what is distilled water?

A

Water that has been heated to form a vapour and has been condensed back to a liquid

Contains less impurities

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10
Q

Why is distilled water used in practical impurities

A

High purity

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11
Q

What do we use water for?

A
  1. Domestic uses - drinking, cooking, gardening
  2. Agriculture use - Frink for animals and crops
  3. Industrial use - Solvent, coolant
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12
Q

Where is water found?

A

Natural sources as lakes, tigers and underground water sources

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13
Q

What is a rock that stores water called?

A

Aquifer

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14
Q

what does water from natural sources come from?

A
  • dissolved oxygen
  • metal compounds
  • plastics
  • sewage
  • harmful microbes
  • nitrates from fertilizers
  • phosphates from fertilizers and detergents
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15
Q

What are examples of beneficial substances in water?

A
  1. Dissolved oxygen - essential for aquatic life
  2. Metal compounds - essential minerals for life, magnesium and calcium
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16
Q

What are examples of harmful substances in water?

A
  1. Metal compounds - toxic, aluminum and lead
  2. Plastic - harmful to aquatic life
  3. Sewage - harmful microbes
  4. Nitrate & phosphate fertilizers - promotes growth which leads to deoxygenation of water.
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17
Q

What does unreacted water contain?

A

Soluble and insoluble impurities

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18
Q

What do soluble and insoluble impurities include?

A

Insoluble - soil, pieces of plants, organic matter

Soluble - dissolved calcium, metallic compounds, inorganic pollutants

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19
Q

What is the water treatment process?

A
  1. Water is pumped into sedimentation tanks where water is allowed to stand for a few hours
  2. Mud sand particles fall to bottom of tank due to gravity, called sedimentation
  3. Filtration - removes smaller particles by passing water through layers of sand and gravely trapped in filter
  4. Water is passed through carbon (as charcoal) to remove taste and odours
  5. Bacteria & microorganism removed by chlorination where chlorine is added to water
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20
Q

what’s the examples of bacterial diseases caused by untreated water?

A

Cholera and typhoid

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21
Q

What elements do fertilizers contain?

A

nitrogen, potassium, phosphorous (NPK)

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22
Q

What is the use of NPK in fertilisers?

A
  1. Nitrogen - makes chlorophyll and protein
  2. Potassium - promotes growth & healthy fruit and flowers
  3. Phosphorous - healthy roots
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23
Q

What are the fertilizer compounds that contain water soluble ions?

A
  • Ammonium ions (NH4+) & nitrate ions (NO3-)
  • phosphate ions (PO43-)
  • potassium ions (K+)
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24
Q

What do common fertilizers compound include?

A

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

25
Q

What is the composition of gasses in air in unpolluted air?

A

Oxygen - 21%
Nitrogen - 78 %
Argon - 0.9 %
CO2 - 0.04 %

26
Q

What are the uses of the gases?

A
  • argon is used in light bulbs
  • oxygen is used in steel making, welding, and breathing apparatus
  • nitrogen is used in food packaging
27
Q

How are oxygen and nitrogen seperated?

A

Fractional distillation

28
Q

How can the percentage of oxygen in air tested?

A

Investigated by passing a known quantity of air over a metal.

29
Q

What happens to the oxygen blown over a metal?

A
  • oxygen in air reacts with metal forming metal oxide.
  • oxygen can be removed from air, volume of air with oxygen can be removed.
30
Q

What gases are produced due to air pollution?

A
  1. Carbon dioxide
  2. Carbon monoxide
  3. Methane
  4. Sulfur dioxide
  5. Particulates
  6. Oxides of nitrogen
31
Q

What are the sources and adverse effects of carbon dioxide?

A

Sources: Complete combustion of carbon containing fuels such as fossil fuels

Adverse effects: Increases global warming, which leads to climate change

Complete combustion (Methane): CH4+ 2O2 —> CO2 + 2H2O

32
Q

What are the sources and adverse effects of carbon monoxide?

A

Sources: Incomplete combustion of carbon - containing fuels such as fossil fuels

Incomplete combustion of gasoline:
C8H18 + 9O2 —> 5CO2 + 2CO2 + 9H2O

Adverse effect: Toxic, combining with hemoglobin prevents from carrying oxygen

33
Q

What are the sources and adverse effects of Particulates?

A

Sources: Incomplete combustion of carbon containing fuels, fossil fuels produce particulates of carbon (soot), e.g the incomplete combustion of methane can produce CO and C:

2CH4 + 3O2→ 2CO + 4H2O

CH4 + O2→ C + 2H2O

Adverse effects: respiratory problems and cancer

34
Q

What are the sources and adverse effects of methane?

A

Sources: waste gases from digestive processes of animals, decomposition of vegetation, bacterial action in swamps, rice paddy fields and landfill sites

Adverse effects: increases global warming, which leads to climate change

35
Q

What are the sources and adverse effects of oxides of nitrogen ?

A

Sources: reaction of nitrogen with oxygen in the presence of high temperatures, e.g. in car engines

  • high-temperature furnaces and when lightning occurs. It is also a product of bacterial action in the soil

Adverse effects:
- Produces photochemical smog

  • Dissolves in rain to form acid rain which causes corrosion to metal structures, buildings and statues made of carbonate rocks, damage to aquatic organisms.
  • Pollutes crops and water supplies, irritates lungs, throats and eyes and causes respiratory problems
36
Q

What are the sources and adverse effects of sulfur dioxide ?

A

Sources: combustion of fossil fuels containing sulfur compounds. Power stations are a major source of sulfur dioxide

Adverse effects: dissolves in rain to form acid rain with similar effects as the acid rain caused by oxides of nitrogen

37
Q

How is greenhouse effect caused by the thermal energy from sun?

A
  • Sun emits energy in the form of radiation that enters the Earth’s atmosphere
  • Some thermal energy is reflected from the Earth’s surface
  • Most thermal energy is absorbed and re-emitted back from the Earth’s surface
  • The energy passes through the atmosphere where some thermal energy passes straight through and is emitted into space
  • But some thermal energy is absorbed by greenhouse gases such as carbon dioxide and methane and is re-emitted in all directions
  • This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm
38
Q

What happens when concentration of greenhouse gases increases?

A
  • more thermal energy is trapped within the Earth’s atmosphere causing the Earth’s average temperature to rise.
  • Called enhanced greenhosue effect
39
Q

What are the consequences of global warming?

A
  • increase in Earth’s temperature
  • water levels will rise as glaciers melt because of high temperatures, causing flooding
  • Extinction of species
  • migration of species
  • spread of diseases
  • loss of habitat
40
Q

Why does production of greenhouse gases needs to be reduced drastically?

A

avoid or at least slow climate change

41
Q

How can CO2 emissions be reduced?

A

using hydrogen and renewable energy supplies such as solar or wind energy instead of burning fossil fuels

42
Q

How can we decrease the methane emission?

A

Reducing the amount of livestock farming

43
Q

How do we remove more carbon dioxide from atmosphere?

A

Planting more trees

44
Q

How is acid rain caused?

A

Oxides of nitrogen and sulfur dioxide

45
Q

What are the effects of acid rain?

A

Reduced by decreasing the amount of oxides of nitrogen and sulfur dioxide

46
Q

What can be used to remove oxides of nitrogen?

A

Catalytic converter

47
Q

How can the emission of sulfur dioxide be reduced?

A
  • using fuels which contain low levels of sulfur
  • Flue gas desulfurization - involves reacting sulfur dioxide emitted from burning fuels containing sulfur with calcium oxide removing it from flue gas.
48
Q

How are oxides of nitrogen formed?

A
  • NO and NO2
  • High pressure
  • temperature
  • maintain conditions of internal combustion engines
49
Q

What do exhaust gases contain?

A
  • Unburned hydrocarbon
  • carbon monoxide
50
Q

What do catalytic converts contain?

A

Series of transition metal catalysts including platinum and rhodium

51
Q

How are metal catalysts?

A

Honeycomb within converter to increase SA

52
Q

what is the chemical equation when carbon monoxide is oxidised to carbon dioxide?

A

2CO + O2 –> 2CO2

53
Q

what are the chemical equations when oxides of nitrogen are reduced to N2?

A

2NO –> N2 + O2
2NO2 –> N2 + 2O2

54
Q

What is the chemical reaction of nitrogen monoxide and carbon monoxide with a catalytic converter?

A

2NO + 2CO –> N2 + 2CO2

55
Q

What is the chemical equation of unburned hydrocarbons that are oxidised to carbon dioxide and water?

A

C8H18 + 12 1/2 O2 –> 8CO2 + 9H2O

56
Q

What is photosynthesis?

A

Endothermic reaction in which energy is transferred from the environment to the chloroplasts in green plants to make glucose.

57
Q

What are the reactants and products for the process of photosynthesis?

A

reactants: Carbon dioxide & water
Products: Glucose and oxygen

58
Q

What is the word equation of photosynthesis?

A

Carbon dioxide + water –(chlorophyll & light)–> glucose + oxygen

59
Q

What is the symbol equation of photosynthesis?

A

6CO2 + 6H2O –> C6H12O6 + 6O2

Chemistry - IGCSE (24 decks)

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