Science 30 - Chemical Energy and Acid Deposition Study Guide

Formation and Maturation of Coal

• Initial Biological Decomposition: The process begins in swampy areas where organic material dies and undergoes initial decomposition by aerobic bacteria.

• Anaerobic Transition: Once the material is covered by sediment, anaerobic bacteria take over the decomposition process, leading to the formation of peat.

• The Maturation Process: The duration of burial is directly proportional to the density and quality of the coal. Longer burial periods expose the organic matter to increased heat and pressure, increasing its maturation degree (coal rank) and decreasing its water and volatile content.

• Coal Ranks and Chemical Composition:

  • Peat: Approximately $60\%$ Carbon, $>53\%$ Volatiles, and $>75\%$ Water content.
  • Brown Coal (Lignite): $60\text{ to }70\%$ Carbon, $53\text{ to }49\%$ Volatiles, and $35\text{ to }10\%$ Water content.
  • Sub-bituminous: $71\text{ to }77\%$ Carbon, $48\text{ to }40\%$ Volatiles, and $25\text{ to }10\%$ Water content.
  • Bituminous: $78\text{ to }87\%$ Carbon, $40\text{ to }20\%$ Volatiles, and $10\text{ to }3\%$ Water content.
  • Anthracite: $>88\%$ Carbon, $<20\%$ Volatiles, and $<5\%$ Water content.

Extraction of Coal

• Mining Methods:

  • Surface Mining: Occurs when coal is less than $200\text{ feet}$ from the surface. This includes strip mining, open-pit mining, and mountaintop removal. It is generally safer and cheaper but results in significant environmental disruption.
  • Underground Mining: Used for deeper deposits; however, it can leave behind toxic tailings from the separation process.

• Alberta Context: Alberta primarily utilizes surface mining. Companies are legally required to reclaim the land after mining operations are complete.

Formation of Petroleum and Natural Gas

• Biological Origin: Small marine organisms (sea plants and animals) die and sink to the sea floor, where they are buried by sediment and rock over $300\text{ to }400\text{ million years}$.

• Sedimentary Basins: As prehistoric seas dried up, sedimentary basins formed. In the absence of oxygen and under extreme heat and pressure, organic matter turned into a waxy substance called kerogen.

• Hydrocarbon Conversion: Continued heat and pressure over $50\text{ to }100\text{ million years}$ convert kerogen into various hydrocarbons (oil and natural gas).

• Geological Traps: For petroleum to accumulate without escaping, it must be trapped beneath an impermeable rock layer (top seal), often within porous sedimentary rock.

Extraction Techniques for Petroleum and Natural Gas

• Reservoirs: Conventional gas and oil are reached by drilling through sedimentary layers into traditional permeable reservoirs.

• Unconventional Sources:

  • Tight Gas: Natural gas held in low-permeability rock.
  • Shale Gas: Gas trapped within mature source rock that has not migrated.
  • Coalbed Methane: Natural gas (methane) trapped within coal deposits. Historically vented as waste, it is now extracted for value using submersible pumps to manage processed water.

• Oil Sands (Tar Sands):

  • Composition: A mixture of sand, water, and bitumen (a thick, viscous petroleum).
  • Mining vs. In Situ: $20\%$ of reserves are shallow enough for surface mining. $80\%$ are deep and require In Situ methods, specifically steam injection, to melt the bitumen so it can be pumped.
  • Tailing Ponds: Reservoirs that hold the water and toxic residue left over from separating bitumen from sand. Alberta houses the largest oil sand reservoir.

• Hydraulic Fracturing (Fracking):

  • Process: Involves injecting high-pressure fluids to create cracks in low-permeability rock to extract tight oil or gas.
  • Seismic Link: Fracking has been linked to Earthquakes in Alberta, some exceeding $4.0\text{ on the Richter scale}$.
  • Monitoring: The AER (Alberta Energy Regulator) tracks these events and enforces specific protocols in Fox Creek, Red Deer, and Brazeau.

Atmospheric Pollutants: Sources and Effects

• Carbon Monoxide ($CO$): Created by incomplete combustion of fuels (primarily road transport). It reduces the oxygen-carrying capacity of blood and reacts to produce ozone.

• Carbon Dioxide ($CO_2$): Emitted from burning fossil fuels for electricity and natural processes; linked to anthropogenic global warming.

• Nitrogen Oxides ($NO_x$): Created by high-temperature combustion in road transport. Nitrous oxide contributes to global warming, while nitrogen dioxide contributes to ground-level ozone and smog.

• Sulfur Dioxide ($SO_2$): Primarily from burning fossil fuels for electricity and metal refining. Reacts with water to create acid rain and causes respiratory distress.

• Ammonia ($NH_3$): Sources include agriculture (manure and fertilizers). It enriches ecosystems with nitrogen and helps produce particulate matter.

• Volatile Organic Compounds (VOCs): Emitted by vegetation, solvents, and road transport. Major contributors to smog and ground-level ozone.

• Ozone ($O_3$): Beneficial in the stratosphere but a major pollutant at ground level (smog), formed in the presence of sunlight.

• Particulate Matter ($PM_{10}, PM_{2.5}$): Tiny solids or droplets that cause haze and lung disease. $PM_{2.5}$ refers to particles smaller than $2.5\,\mu m$.

• Heavy Metals: Includes Mercury ($Hg$), Lead ($Pb$), Cadmium ($Cd$), and Arsenic ($As$). These result from fuel combustion and have severe toxic health impacts (e.g., Grassy Narrows mercury contamination).

The Carbon Cycle and Combustion

• Combustion as a Cycle Component: Combustion returns stored carbon ($CO_2$) to the atmosphere. Levels have risen steadily since the Industrial Revolution.

• Historical Context: John Tyndall proved heat-trapping by $CO_2$ in the $1860\text{s}$.

• The Keeling Curve: Shows annual cycles of $CO_2$ (rising in fall/winter due to lack of photosynthesis and dropping in spring/summer). The overall trend remains upward.

• Types of Combustion:

  • Complete Combustion: Hydrocarbon burns in unlimited oxygen. Products: $H_2O(g)$ and $CO_2(g)$.
  • Incomplete Combustion: Limited oxygen supply. Products: $H_2O(g)$, $CO(g)$, and/or Carbon (soot). $CO$ binds strongly to hemoglobin, blocking oxygen.

Thermodynamics and Chemical Potential Energy

• Efficiency Formula: $\text{Percent Efficiency} = \frac{\text{Work Output}}{\text{Energy Input}} \times 100\%$.

• Heat of Combustion ($\Delta H$): The amount of heat released when a substance burns. Released because reactants have more bond energy than products.

• Exothermic Reactions: Characterized by a negative $\Delta H$. Potential energy of products is lower than reactants.

• Calorimetry: An experimental process used to measure temperature changes in water to determine the energy of reactions (Bomb calorimeters and coffee-cup calorimeters).

• Hess’s Law: The theoretical heat of reaction ($\Delta H_r$) is calculated by comparing standard heats of formation ($\Delta H_f^\circ$). Principal elements have a $\Delta H_f^\circ$ of zero.

  • Equation: $\Delta H_r = \sum n\Delta H_f^\circ(\text{products}) - \sum n\Delta H_f^\circ(\text{reactants})$
  • Example (Methane): $CH_4(g) + 2O_2(g) \rightarrow CO_2(g) + 2H_2O(g)$

Sulfur and Nitrogen Oxide Specifics

• Sulfur Oxides ($SO_x$):

  • Natural Sources: Hot springs and volcanic activity.
  • Sour Gas: Natural gas containing Hydrogen Sulfide ($H_2S$). Approximately $1/3$ of Alberta’s gas is sour.
  • Sweetening: Amines remove $H_2S$; the Claus process converts it to elemental sulfur.
  • Flaring: Burning sour gas to release $SO_x$: $H_2S(g) + O_2(g) \rightarrow SO_2(g) + H_2O(g)$.

• Nitrogen Oxides ($NO_x$):

  • Formation: Nitrogen gas ($N_2$) makes up $78\%$ of the atmosphere. High combustion temperatures cause atmospheric $N_2$ to react with oxygen.
  • Reaction Sequence: $N_2(g) + O_2(g) \rightarrow 2NO(g)$, then $2NO(g) + O_2(g) \rightarrow 2NO_2(g)$.

Properties of Solutions

• Dissociation: Ionic compounds dissolve in water, releasing ions. These are electrolytic (conduct electricity).

• Molecular Solutions: Usually non-electrolytic. Solubility depends on polarity.

• Acids vs. Bases:

  • Acids: Red litmus, sour taste, reacts with metals to produce $H_2(g)$, electrolytic.
  • Bases: Blue litmus, bitter taste, slippery feel, corrosive, electrolytic.

The pH Scale and Indicators

• Definition: A logarithmic measure of hydronium ion concentration $[H_3O^+]$.

  • Formulas: $pH = -\log[H_3O^+]$ and $[H_3O^+] = 10^{-pH}$.
  • Scale: Neutral is $7$. Acids are $< 7$, bases are $> 7$. A change of $1$ on the scale is a tenfold change in concentration.

• Indicators: Chemicals that change color at specific pH ranges (e.g., Methyl orange, Methyl red, Bromothymol blue).

Acid-Base Theories

• Arrhenius Definition:

  • Acids: Dissociate to release $H^+$ (e.g., $HA \rightarrow H^+(aq) + A^-(aq)$).
  • Bases: Dissociate to release $OH^-$ (e.g., $MOH \rightarrow M^+(aq) + OH^-(aq)$).
  • Limitations: It cannot explain why $NH_3$ acts as a base or why $H^+$ exists (it actually forms $H_3O^+$).

• Bronsted-Lowry Definition:

  • Acid: Proton ($H^+$) donor.
  • Base: Proton ($H^+$) acceptor.
  • Conjugates: Products formed after the transfer (Conjugate Acid and Conjugate Base).

Titration Logic and Strength

• Acid Strength: Describes the percentage of ionization in water. Strong acids ionize $100\%$. Weak acids ionize very little. Strength is different from concentration.

• Technique: Using a burette to add a known concentration solution to an unknown until the endpoint (color change) is reached.

• Calculation: Use $n = C \times V$ to find moles, then use mole ratios to find the unknown concentration.

Acid Deposition: Causes and Effects

• Formation Reactions:

  • $SO_2(g) + H_2O(l) \rightarrow H_2SO_3(aq)$
  • $SO_3(g) + H_2O(l) \rightarrow H_2SO_4(aq)$
  • $2NO_2(g) + H_2O(l) \rightarrow HNO_2(aq) + HNO_3(aq)$

• Deposition Types: Wet (rain, snow) and Dry (gases/particles landing on surfaces and later reacting with water).

• Buffering: Basic substances like Carbonates in water neutralize acidity: $H_3O^+(aq) + CO_3^{2-}(aq) \rightarrow H_2O(l) + HCO_3^-(aq)$. Buffering capacity is not infinite.

• Leaching: Soil acidity dissolves insoluble minerals like Aluminum ($Al^{3+}$), which damages roots and hinders nutrient uptake.

• Biomagnification: Toxins like mercury increase in concentration as they move up the food chain.

Mitigation Technologies

• Electrostatic Precipitation: Uses negative charges to extract fly ash and particulates from air.

• Scrubbers: Removes $SO_2$ from emissions by reacting it with Calcium Carbonate or Lime ($CaO$), often producing gypsum ($CaSO_4$).

• Catalytic Converters: Used in cars to convert $NO_x$ into $N_2$, and $CO$/hydrocarbons into $CO_2$ and $H_2O$. Platinum ($Pt$), Palladium ($Pd$), and Rhodium ($Rh$) are common catalysts.

• Environmental Correction: Liming involves adding $CaO$ or $CaCO_3$ to acidic lakes or soils to neutralize pH.