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Oxygen and air by marium farooq
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Oxygen and air by marium farooq


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  • 1.  Air and oxygen Mariam Farooq
  • 2. •The atmosphere is a layer of air containing mixture of several gases. This mixture composition varies according to time and place. •The composition of water vapour varies from 0-5%, depending on the humidity of air.
  • 3. •A known volume of air is passed through tube with burning copper powder •Oxygen in air will react with hot copper powder to produce black copper oxide: 2Cu(s) + O2(g) --> 2CuO(s)
  • 4. After the reaction is complete it is found that the volume of air decreases to 79 cm3 This means that 21 cm3 has been used up by the copper. This represents the percentage of oxygen in the air. Volume of O2 = Initial volume of air – Final volume of air Volume of O2 = 100 cm3 – 79 cm3 Volume of O2 = 21 cm3 % Volume of O2 = 21 cm3 / 100 cm3 * 100 21%
  • 5. Dust free air is pumped into the plant Carbon dioxide is removed by bubbling through an alkali Water is removed in a drying tower. Gases are compressed to 200 atmospheres. Expansion of gases.
  • 6. Liquid air to a fractionating tower. Nitrogen gas Oxygen gas Repeated expansion and compression of gases. The first gas to boil off is NITROGEN, at -196oC When all the nitrogen has been given off, the temperature rises to -186oC where ARGON gas boils off. OXYGEN comes next, at -183oC . The gases are boiled off separately and are collected and stored under pressure in cylinders.
  • 7. A. Respiration Oxygen is essential for all plant and animal life on earth. The process by which living organisms produce energy from their food is called respiration. Oxygen is essential for this process: sugar + oxygen ---> carbon dioxide + water + energy
  • 8. B. Combustion/Burning 3 things are required for combustion fuel heat Oxygen MOST substances react with O2 to in exothermic reaction, which is called combustion. If flames are produced during combustion, it’s called burning. ALL carbon compounds burn in O2 to produce CO2 while ALL hydrogen containing compounds burn in O2 to produce H2O. When adequate supply of oxygen is available during burning, it will create a complete combustion. If otherwise, the combustion is incomplete. E.g. CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g), makes up a complete combustion
  • 9. Oxygen is a reactive gas and will combine directly with most metals and non-metals to form oxides Reaction with metals: Most metals, except silver and gold, combine directly with oxygen to form metal oxides. Most metal oxides are basic oxides ; those that dissolve in water form alkalis. Eg: sodium + oxygen sodium oxide 4 Na + O2 2Na2O sodium oxide + water sodium hydroxide Na2O + H2O 2NaOH
  • 10. Reaction with non-metals non-metals like carbon, sulphur and phosphorus burn in oxygen to form acidic oxides. Eg: carbon + oxygen carbon dioxide C + O2 CO2 Carbon dioxide + water carbonic acid CO2 + H2 O H2CO3 On Pg # 278 of your chemistry book
  • 11. All around the Earth there is a thick blanket of air called the atmosphere. Although the composition of air is reasonably constant , there are some gases like carbon monoxide, CO, Sulphur dioxide,SO2, and oxides of Nitrogen, NO , which when introduced into the atmosphere, are not removed. As they are poisonous they are therefore termed as pollutant gases.
  • 12. 1) Carbon monoxide, CO Comes from: - When fuels like petrol and diesel are burnt in an internal combustion engine, the amount of oxygen present is limited, so carbon monoxide gas is formed, instead of carbon dioxide gas. - Unburnt hydrocarbons - forest fires Hazards: - Combines with haemoglobin when inhaled, which produces carboxyhaemoglobin that reduces efficiency of haemoglobin to transport oxygen. - Cells then die. Prevention: - Install catalytic converters in cars - Reduce number of cars on road - Create efficient engines in cars to ensure complete hydrocarbon combustion
  • 13. 2) Sulphur dioxide, SO2 Comes from: - Combustion of fossil fuels containing sulphur impurities - volcanic eruptions Hazards: - Lung irritant - eye irritant - acid rain Prevention: - Prevent using fuels containing sulphur impurities, e.g. coal - Reduce the sulphur impurities inside fossil fuels - Spray exhaust gases from factories with water/hydrated CaO/alkalis to absorb sulphur dioxide before it’s released into the atmosphere - Add CaO to soil and rivers to neutralize acid rain
  • 14. 3) Oxides of nitrogen, NO Comes from: - Lightning activity - forest fires - internal combustion engines (as nitrogen oxides are formed by oxygen and nitrogen under high temperature) --> Poisonous oxides of nitrogen are also formed from the electrical spark which passes through the air/petrol mixture. - power stations Hazards: - Eutrophication - lung damage - acid rain Prevention: - Install catalytic converters in cars - Design car engines which run at lower temperatures
  • 15. Notes: Reactions of oxides of sulphur and nitrogen The oxides of sulphur and nitrogen are acidic gases and are water-soluble. They dissolve to form acid rain.The main source of these pollutant gases is from the burning of fuels, especially those in petrol and diesel engines. All oils and fuels contain sulphur,and when they are burnt, sulphur dioxide gas is formed. In power stations, large quantities of this gas are produced, which dissolve in water in the atmosphere to form sulphurous acid (sulphuric acid) SO2 (g) + H2O (l) --> H2SO3 (aq)
  • 16. Ozone at the ground level can damage plants and gives discomfort to the nose, throat an d chest in humans. This can irritate the lungs.