Maintaining Air Quality 22 - Chemistry Past Paper PDF

Maintaining Air Quality 22 Your Chemistry Teacher, Mr. Aaron Tang  Composition of Air Air is a mixture of several gases. The volume composition of gases in dry air includes: 78% ________ nitrogen (N2) 21% ________ oxygen (O2) ~ 0.9% argon (Ar)...

Maintaining Air Quality 22 Your Chemistry Teacher, Mr. Aaron Tang  Composition of Air Air is a mixture of several gases. The volume composition of gases in dry air includes: 78% ________ nitrogen (N2) 21% ________ oxygen (O2) ~ 0.9% argon (Ar) ________ ~ 0.1% carbon dioxide and other gases (e.g. neon, helium) ________ How do we determine the composition of air? What gas in the air would react with the heated copper powder? oxygen. 2Cu + O2 --> 2CuO State one observation you see in this experiment. the reddish brown copper turns black Why must air be passed over heated copper powder until there is no further decrease in volume? To ensure that there is no more oxygen left in the air, i.e. all oxygen has reacted. Why must the apparatus be allowed to cool to room temperature before the total volume of gas left in the syringes is measured? To ensure that there is no expansion of gas due to the increase in temperature. How do we determine the composition of air? 80 cm3 of air were passed over the heated copper in the tube until there was no further decrease in volume. On cooling to room temperature, only 64 cm3 of gas remained. Determine the percentage of oxygen in air. volume of oxygen in air = 80 – 64 = 16 cm3 Percentage of oxygen in air = 16/80 x 100% = 20% Fractional distillation of Air Nitrogen (b.p.: -196oC) ion tillat remove H2O and CO2 Argon l dis Air Liquid Air (b.p.: -186oC) iona cooling & compression fract Oxygen (b.p.: -183oC) Oxygen, nitrogen and noble gases in the air can be separated by _____________________ fractional distillation of liquid air. Why are carbon dioxide and water are removed prior to liquefaction? If CO2 and H2O are not removed, they would change to ice and dry ice respectively and block the pipes in the cooling system.  Air Pollutants Air Pollution is _________________________ introduction of unwanted and harmful _____________________________________ chemicals into the atmosphere Air pollutants are also known as atmospheric pollutants, and are harmful gases that should not be found in a sample of clean air. They frequently cause harm to the environment or living things.  Sulfur Dioxide fossil fuels corrodes bridges motor vehicles biodiversity eyes lungs breathing in ammation fl  Sulfur Dioxide calcium hydroxide / oxide calcium carbonate Ca(OH)2 + H+ ——> Ca2+ + H2O CaCO3 + H+ ——> Ca2+ + CO2 + H2O oil natural gas coal Calcium carbonate CaCO3 (s) ——> CaO (s) + CO2 (g) CaO (s) + SO2 (g) ——> CaSO4 [calcium sulfate]  Oxides of Nitrogen lightning activity N2 (g) + O2 (g) ——> 2NO (g) 2NO (g) + O2 (g) ——-> 2NO2 (g) corrodes bridges motor vehicles biodiversity eyes lungs breathing in ammation ozone fl Oxides of Nitrogen calcium hydroxide / oxide calcium carbonate Ca(OH)2 + H+ ——> Ca2+ + H2O CaCO3 + H+ ——> Ca2+ + CO2 + H2O catalytic converters nitrogen 2CO (g) + 2NO (g) ——-> 2CO2 (g) + N2 (g) Acid Rain [Info] CO2 (g) + 2H2O (l) ——> H2CO3 (aq) (carbonic acid – weak acid) Rain water is naturally slightly _______________, acidic due to dissolved carbon dioxide. However, acid rain is much more acidic (pH H2SO3(aq) (1) 2NO2(g) + H2O(l) -> HNO3(aq) + HNO2(aq) (2) 2H2SO3(aq) + O2(g) -> 2H2SO4(aq) (2) 2HNO2(aq) + O2(g) -> 2HNO3(aq) sulfuric acid nitric acid Carbon Monoxide incomplete carbon soot haemoglobin headaches breathing dif culties death catalytic converters oxidised carbon dioxide fi Unburnt Hydrocarbons photochemical smog ozone sulfur dioxide nitrogen dioxide eye and respiratory tract irritation catalytic converters carbon dioxide water vapour Methane (CH4) bacterial plant animal global warming heat sun melt rise climate  Ozone sunlight nitrogen dioxide unburnt hydrocarbons photosynthesis chest pains and headaches nitrogen dioxide unburnt hydrocarbons Catalytic Converters exhaust platinum (Pt) palladium (Pd) rhodium (Rd) CO CO2 CxHy H2O NOx N2 redox 2NO (g) + 2CO (g) —> N2 (g) + 2CO2 (g) 2C8H18 (g) + 25O2 (g) —> 16CO2 (g) + 18H2O (g) Catalytic Converters honeycomb redox carbon dioxide + nitrogen 2NO (g) + 2CO (g) —> N2 (g) + 2CO2 (g) carbon dioxide 2CO (g) + O2 (g) —> 2CO2 (g) nitrogen + oxygen 2NO2 (g) —> N2 (g) + 2O2 (g) 2C8H18 (g) + 25O2 (g) —> 16CO2 (g) + 18H2O (g) Flue Gas Desulfurisation fossil fuels sulfur dioxide calcium carbonate calcium sul te + carbon dioxide CaCO3 (s) + SO2 (g) ——> CaSO3 (s) + CO2 (g) calcium sulfate *CaSO3 (s) + O2 (g) ——> CaSO4 (s) gypsum calcium carbonate calcium oxide fi Flue Gas Desulfurisation space expensive low sulfur  The Ozone Layer allotrope photochemical ozone ultraviolet (UV) rays Chloro uorocarbons (CFCs) CFCl3 CF2Cl2 aerosol propellants coolant uids plastics broken down sunlight chlorine ozone chlorine fl fl The Ozone Layer skin cancer plants marine life UV Rays stop / minimise The Ozone Layer One chlorine radical can destroy a lot of ozone!  Carbon Cycle processes carbon dioxide photosynthesis combustion respiration CH4(g) + 2O2 (g) —> CO2 (g) + H2O (g) glucose carbon dioxide oxygen 6CO2 (g) + 6H2O (l) —> C6H12O6(aq) + 6O2 (g) sugars oxidises C6H12O6(aq) + 6O2 (g) —> 6CO2 (g) + 6H2O (l) fossil fuels Combustion Calcium Carbonate Carbon Cycle  Global Warming Carbon dioxide Methane global warming greenhouse effect  Global Warming Climate Change rainfall bleached carbonate rise