11. Chemistry of the environment Flashcards
Chemical tests for the presence of
water and how to test for the purity of water
anhydrous copper sulphate turns blue from white
anhydrous cobalt chloride turns pink from blue
pure- 100 boiling 0 melting
impure- BP greater, MP lower
Why is distilled water used in practical chemistry
distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities
Water from natural sources may
contain substances, including:
(a) dissolved oxygen
(b) metal compounds
(c) plastics
(d) sewage
(e) harmful microbes
(f) nitrates from fertilisers
(g) phosphates from fertilisers and detergents
Some of these substances are
beneficial and some are harmful, including:
(a) dissolved oxygen for aquatic life
(b) some metal compounds provide essential minerals for life
(a) some metal compounds are toxic
(b) some plastics harm aquatic life
(c) sewage contains harmful microbes which cause disease
(d) nitrates and phosphates lead to deoxygenation of water and damage to aquatic life
Describe the treatment of the domestic water
(a) sedimentation and filtration to remove solids
(b) use of carbon to remove tastes and odours
(c) chlorination to kill microbes
Fertilisers elements and uses
ammonium salts and nitrates are used as fertilisers
nitrogen- makes chlorophyll and protein and promotes green healthy leaves
phosphorus- promotes healthy roots
potassium- promotes growth and healthy fruits and flowers
Composition of clean, dry air
78% nitrogen, 21% oxygen, argon- 0.9% and carbon dioxide, 0.04% and the remainder is a mixture of noble gases
source of each of these air pollutants
(a) carbon dioxide from the complete combustion of carbon-containing fuels
(b) carbon monoxide and particulates from the incomplete combustion of carbon-containing fuels
(c) methane from the decomposition of vegetation and waste gases from digestion in animals
(d) oxides of nitrogen from car engines
(e) sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds
Adverse effect of these air pollutants
(a) carbon dioxide: higher levels of carbon dioxide leading to increased global warming, which leads to climate change
(b) carbon monoxide: toxic gas
(c) particulates: increased risk of respiratory problems and cancer
(d) methane: higher levels of methane leading to increased global warming, which leads to climate change
(e) oxides of nitrogen: acid rain, photochemical smog and respiratory problems
(f) sulfur dioxide: acid rain
Describe how the greenhouse gases carbon dioxide and methane cause global warming
(a) the absorption, reflection and emission of thermal energy
(b) reducing thermal energy loss to space
State and explain strategies to reduce the effects of these environmental issues
a) climate change: planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and
renewable energy, e.g. wind, solar
(b) acid rain: use of catalytic converters in vehicles, reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurisation with calcium oxide
how oxides of nitrogen form in car engines and describe their removal by catalytic converters.
Catalytic converter reaction
nitrogen gas and oxygen gas from air react in high temperature and pressure in car engines.
catalytic converters contain catalysts like platinum and rhodium in a honeycomb within structure to increase surface area.
nitrogen(II)oxide + carbon monoxide => nitrogen + carbon dioxide
2CO + 2NO → 2CO2 + N2
Photosynthesis process and reaction
the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2