Ch 17 - (Chemistry of our environment) Flashcards
What is used to test for water?
- Cobalt (II) chloride
- Copper (II) sulfate
How is the test for cobalt chloride done?
using cobalt chloride paper
what is the word equation for cobalt (II) chloride?
Anhydrous cobalt (II) chloride + water –> <– hydrated cobalt (II) chloride
what is the symbol equation for cobalt (II) chloride?
CoCl2 (s) + 6H2O (l) –> <– CoCl2.6H2O (s)
what is the word equation for copper (II) sulfate?
Anhydrous copper (II) sulfate + water –> <– hydrated copper (II) sulfate
what is the symbol equation for copper (II) sulfate?
CuSO4 (s) + 6H2O (l) –> <– CuSO4.5H2O (s)
What is the positive test for water in copper sulfate and cobalt chlroide?
cobalt (II) chlroide: Blue to pink
Copper (II) sulfate: White to blue
What can be used to test for the purity of a substance?
Melting point and boiling point
what is distilled water?
Water that has been heated to form a vapour and has been condensed back to a liquid
Contains less impurities
Why is distilled water used in practical impurities
High purity
What do we use water for?
- Domestic uses - drinking, cooking, gardening
- Agriculture use - Frink for animals and crops
- Industrial use - Solvent, coolant
Where is water found?
Natural sources as lakes, tigers and underground water sources
What is a rock that stores water called?
Aquifer
what does water from natural sources come from?
- dissolved oxygen
- metal compounds
- plastics
- sewage
- harmful microbes
- nitrates from fertilizers
- phosphates from fertilizers and detergents
What are examples of beneficial substances in water?
- Dissolved oxygen - essential for aquatic life
- Metal compounds - essential minerals for life, magnesium and calcium
What are examples of harmful substances in water?
- Metal compounds - toxic, aluminum and lead
- Plastic - harmful to aquatic life
- Sewage - harmful microbes
- Nitrate & phosphate fertilizers - promotes growth which leads to deoxygenation of water.
What does unreacted water contain?
Soluble and insoluble impurities
What do soluble and insoluble impurities include?
Insoluble - soil, pieces of plants, organic matter
Soluble - dissolved calcium, metallic compounds, inorganic pollutants
What is the water treatment process?
- Water is pumped into sedimentation tanks where water is allowed to stand for a few hours
- Mud sand particles fall to bottom of tank due to gravity, called sedimentation
- Filtration - removes smaller particles by passing water through layers of sand and gravely trapped in filter
- Water is passed through carbon (as charcoal) to remove taste and odours
- Bacteria & microorganism removed by chlorination where chlorine is added to water
what’s the examples of bacterial diseases caused by untreated water?
Cholera and typhoid
What elements do fertilizers contain?
nitrogen, potassium, phosphorous (NPK)
What is the use of NPK in fertilisers?
- Nitrogen - makes chlorophyll and protein
- Potassium - promotes growth & healthy fruit and flowers
- Phosphorous - healthy roots
What are the fertilizer compounds that contain water soluble ions?
- Ammonium ions (NH4+) & nitrate ions (NO3-)
- phosphate ions (PO43-)
- potassium ions (K+)
What do common fertilizers compound include?
Ammonium nitrate (NH4NO3)
Ammonium phosphate (NH4)3PO4
Potassium sulfate (K2SO4)
What is the composition of gasses in air in unpolluted air?
Oxygen - 21%
Nitrogen - 78 %
Argon - 0.9 %
CO2 - 0.04 %
What are the uses of the gases?
- argon is used in light bulbs
- oxygen is used in steel making, welding, and breathing apparatus
- nitrogen is used in food packaging
How are oxygen and nitrogen seperated?
Fractional distillation
How can the percentage of oxygen in air tested?
Investigated by passing a known quantity of air over a metal.
What happens to the oxygen blown over a metal?
- oxygen in air reacts with metal forming metal oxide.
- oxygen can be removed from air, volume of air with oxygen can be removed.
What gases are produced due to air pollution?
- Carbon dioxide
- Carbon monoxide
- Methane
- Sulfur dioxide
- Particulates
- Oxides of nitrogen
What are the sources and adverse effects of carbon dioxide?
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
What are the sources and adverse effects of carbon monoxide?
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
What are the sources and adverse effects of Particulates?
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
What are the sources and adverse effects of methane?
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
What are the sources and adverse effects of oxides of nitrogen ?
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
What are the sources and adverse effects of sulfur dioxide ?
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
How is greenhouse effect caused by the thermal energy from sun?
- 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
What happens when concentration of greenhouse gases increases?
- more thermal energy is trapped within the Earth’s atmosphere causing the Earth’s average temperature to rise.
- Called enhanced greenhosue effect
What are the consequences of global warming?
- 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
Why does production of greenhouse gases needs to be reduced drastically?
avoid or at least slow climate change
How can CO2 emissions be reduced?
using hydrogen and renewable energy supplies such as solar or wind energy instead of burning fossil fuels
How can we decrease the methane emission?
Reducing the amount of livestock farming
How do we remove more carbon dioxide from atmosphere?
Planting more trees
How is acid rain caused?
Oxides of nitrogen and sulfur dioxide
What are the effects of acid rain?
Reduced by decreasing the amount of oxides of nitrogen and sulfur dioxide
What can be used to remove oxides of nitrogen?
Catalytic converter
How can the emission of sulfur dioxide be reduced?
- 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.
How are oxides of nitrogen formed?
- NO and NO2
- High pressure
- temperature
- maintain conditions of internal combustion engines
What do exhaust gases contain?
- Unburned hydrocarbon
- carbon monoxide
What do catalytic converts contain?
Series of transition metal catalysts including platinum and rhodium
How are metal catalysts?
Honeycomb within converter to increase SA
what is the chemical equation when carbon monoxide is oxidised to carbon dioxide?
2CO + O2 –> 2CO2
what are the chemical equations when oxides of nitrogen are reduced to N2?
2NO –> N2 + O2
2NO2 –> N2 + 2O2
What is the chemical reaction of nitrogen monoxide and carbon monoxide with a catalytic converter?
2NO + 2CO –> N2 + 2CO2
What is the chemical equation of unburned hydrocarbons that are oxidised to carbon dioxide and water?
C8H18 + 12 1/2 O2 –> 8CO2 + 9H2O
What is photosynthesis?
Endothermic reaction in which energy is transferred from the environment to the chloroplasts in green plants to make glucose.
What are the reactants and products for the process of photosynthesis?
reactants: Carbon dioxide & water
Products: Glucose and oxygen
What is the word equation of photosynthesis?
Carbon dioxide + water –(chlorophyll & light)–> glucose + oxygen
What is the symbol equation of photosynthesis?
6CO2 + 6H2O –> C6H12O6 + 6O2
