Reference pg and in Textbook

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Neal O’Connor’
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1 Reference pg and in Textbook

2 Combustion Reactions During combustion (burning) of fossil fuels, collisions between the molecules of the fuel and oxygen result in the formation of new molecules. i.e. Combustion of Gasoline 2C 8 H 18 (l) + 25O 2 (g) à 16CO 2 (g) + 18H 2 O(g) + energy

3 The products formed during a combustion reaction are directly related to the atoms present in the substance being combusted Emissions are the substances discharged into the atmosphere due to combustion reactions

4 Oxides of Carbon Burning carbon compounds, like wood, biomass or hydrocarbons (natural gas or gasoline) result in the formation of carbon dioxide. Carbon dioxide is an important part of the carbon cycle (think photosynthesis and cellular respiration)

5 Carbon dioxide is a greenhouse gas, meaning it has the ability to absorb thermal energy. This absorption traps the heat in the atmosphere (preventing the loss of heat into space) and directly effecting the Earth s climate.

6 Carbon monoxide is a common product of incomplete combustion. That is, there is not enough oxygen present in the atmosphere for the reaction to proceed completely. i.e. Incomplete combustion of methane CH 4 (g) + 3O 2 (g) à CO(g) + 4H 2 O(g)

7 Carbon monoxide is a poisonous gas that binds to hemoglobin in your blood, preventing it from binding to oxygen. Emissions testing programs measure the carbon monoxide concentration in vehicle exhaust.

8 Summary Product of Combustion CO(g) CO 2 (g) Source Incomplete combustion of hydrocarbons (fossil fuels) Complete combustion of hydrocarbons (fossil fuels)

9 Reactions of Carbon Oxides Carbon Oxides react with water to form acidic H 2 CO 3 CO 2 (g) + H 2 O(l) à H 2 CO 3 (aq)

10 Oxides of Sulfur Sulfur is an element found in small quantities within fossil fuels

11 Natural gas commonly contains sulfur in the form of hydrogen sulfide (H 2 S) and is known as sour gas. Sour gas is toxic and forms acidic rain, so processing natural gas often includes sweetening, which is the process of reducing H 2 S i.e. Formation of acid rain from hydrogen sulfide H 2 S(g) + 2H 2 O(l) à 2H 3 O + (aq) + S 2- (aq)

12 Flaring (in a gas well) converts hydrogen sulfide into sulfur dioxide and sulfur trioxide emissions Sulfur dioxide and sulfur trioxide can also react with water to produce acid rain H 2 S(g) + O 2 (g) à SO 2 (g) + H 2 O(g) SO 2 (g) + O 2 (g) à SO 3 (g)

13 The combustion of coal also results in the production of sulfur dioxide. The yellow stockpiles near processing plants consist of elemental sulfur The sulfur is combined with metal atoms in refining of metals.

14 Summary Product of Combustion SO 2 (g), SO 3 (g) SO 2 (g) Source Combustion of fossil fuels containing H 2 S and refining of fossil fuels, metal and paper Naturally emitted from hot springs and volcanic outgassing

15 Reactions of Sulfur Oxides Sulfur Oxides react with water to form acidic H 2 SO 3 or H 2 SO 4 SO 2 (g) + H 2 O(l) à H 2 SO 3 (aq) SO 3 (g) + H 2 O(l) à H 2 SO 4 (aq)

16 Oxides of Nitrogen Nitrogen makes up 78.1% of the Earth s atmosphere If the temperature of the combustion process is high enough (above 650C), the normally unreactive nitrogen in the air becomes activated and will react to produce nitrogen oxides such as nitrogen monoxide (NO) and nitrogen dioxide (NO 2 )

17 The most common source of sources of NO x compounds are high-temperature combustion processes which react with water to form acid rain. Studies have shown that higher No x emissions occur in urban areas. N 2 (g) + O 2 (g) à 2NO(g) 2NO(g) + O 2 (g) à 2NO 2 (g)

18 Summary Product of Combustion NO(g), NO 2 (g), NO x (g) Source High temperature combustion reacting with air from the atmosphere containing nitrogen Naturally emitted from forest fires

19 Reaction of Nitrogen Oxides Nitrogen Oxides react with water to form acidic HNO 3 or HNO 2 NO 2 (g) + H 2 O(l) à HNO 3 (aq) + HNO 2 (aq) NO 2 (g) + H 2 O(l) + O 2 (g) à HNO 3 (aq)

20 Metals and Metal Oxides Metal atoms, either in elemental form or as a compound, can also be present in emissions from combustion reactions. For example, coal contains small amounts of lead and mercury.

21 Monitoring Emissions Alberta Environment is involved in programs that monitor and maintain the quality of Alberta s environment to protect the health of citizens and ecosystems. Factors considered when establishing standards for environmental quality include: sensitivity of organisms, behavior of substances in the environment, natural levels, availability of technology to control emissions and ability to detect or monitor emissions.

22 What is Acid Rain?! Acid rain describes the excessive amount of acidity within precipitation. Wind patterns like Jet Streams provide a way for acid deposition to be transported. Acid deposition can be transported short and long distances.

23 Effects of Acid Deposition Most lakes in Alberta contain the carbonate ion CO 2-3 (aq) causing lakes to be naturally basic or alkaline. This alkalinity is from dissolving mineral such as calcium carbonate present in limestone. Limestone in soil is made of calcium carbonate, and the presence of these ions have a great impact on the sensitivity to acid deposition.

24 Reaction of Carbonate ions with Acid ions H 3 O + (aq) + CO 3 2- (aq) à H 2 O(l) + HCO 3- (aq) A small percentage of soils in Canada have a high potential for neutralizing acid deposition due to the presence of carbonate ions.

25 Buffering Capacity The neutralization of acid deposition by bases, such as calcium carbonate prevents the accumulation of hydronium ions or change in ph of the soil is known as buffering. Buffering capacity is a measure of the amount of acid that can be neutralized by soil or surface water.

26 Effect on Plants Few plants can tolerate low ph, therefore it is important for farmers to select crops best suited to the ph of the soil.

27 Ca 2+ Leaching Calcium ions Ca 2+ (aq) are one of the required nutrients for plant growth. The reaction with acid deposition releases calcium ions usually bonded, to be more available to plants. A change in the soil ph can result in the formation of insoluble chlorosis the yellowing of plant leaves due to lack of chlorophyll, caused by nutrient deficiencies in the soil

28 Metal Leaching The addition of acids to soil can make Ca 2+ and Mg 2+ ions being more available to plants. One effect of prolonged acid deposition is the leaching of aluminium ions Al 3+ (aq) and mercury(ii) ions Hg 2+ (aq)

29 Al 3+ Leaching Aluminium ions accumulate over time and can effect plants by decreasing root growth, preventing the absorption of calcium and reducing soil bacteria involved in the decomposition of matter Al 3+ ions are toxic to fish, damaging the gills of older fish and killing young fish.

30 Hg 2+ Leaching Mercury is converted to methyl mercury in soil, a substance that is rapidly absorbed by other organisms, which has no function and cannot be excreted. Since it is not removed, mercury tends to accumulate and cause bioaccumulation (biomagnification) in the food chain.

Science 30 Unit B Chemistry and the Environment

Science 30 Unit B Chemistry and the Environment Outcome 1: Students will analyze the sources of acids and bases and their effects on the environment. Specific Outcome 1.9: Describe impacts on the biotic