chem review pt 2

• Humans rely on the combustion of fuels to provide energy for everyday needs
• Emissions


  Gaseous pollutants released into the air that are carried by wind

  
• Particulates


  Solid particles released into the air
• Combustion reaction


  Hydrocarbon + Oxygen -> Carbon Dioxide + Water

  
• The products of combustion reactions are considered to be anthropogenic and contribute to global warming
• Anthropogenic sources


  • Carbon Dioxide
  • Sulfur Oxides
  • Nitrogen Oxides
  • Carbon Monoxide
  • Particulates
• Natural sources


  • Carbon Dioxide
  • Sulfur Oxides
  • Nitrogen Oxides
  • Particulates
• Reactions in the atmosphere

  1. Carbon Dioxide + Water -> Carbonic acid

  2. Sulfur Dioxide + Water -> Sulfuric acid

  3. Nitrogen Dioxide + Water -> Nitric acid

  
• Environmental impacts of acid deposition include changes in soil pH, washing away of nutrients/minerals, death of aquatic populations, defoliation of plants and trees, increased rates of asthma and bronchitis, and corrosion of buildings
• Buffers


  • Substances that resist changes in pH

  
• Functions that reduce acid deposition

  • Electrostatic precipitator
  • Scrubber
  • Catalytic converter
  • Liming
• Acid


  Substances with a sour taste that change blue litmus to red and react with metals to form hydrogen
• Base


  Substances with a bitter taste that feel slippery, change red litmus to blue, and are conductive
• Bronsted-Lowry acid


  A proton donor
• Bronsted-Lowry base


  A proton acceptor
• Generally, the stronger an acid, the weaker its conjugate base
• As pH decreases (becomes more acidic)


  The concentration of H3O+ ions increases exponentially
• Calculating pH


  pH = -log[H3O+]
• Calculating H3O+ concentration


  [H3O+] = 10^-pH
• Acid/base indicators


  Substances that change colour at specific pH ranges
• Titration


  Add titrant (base) to burette, record initial volume

  2. Pipette solution with unknown acid concentration into flask, add indicator

  3. Titrate base into flask until neutralization (endpoint), record final volume

  4. Repeat until 3 trials within 0.2 mL

  5. Use formula: (Cacid)(Vacid) = (Cbase)(Vbase) to calculate unknown acid concentration

  
• The trick to any test-based assessment is elimination. If you can eliminate options and narrow down the possibilities, you can increase your chance at success.
• Indicator


  A substance used to distinguish between two water samples
• Titration


  A process where a solution of known concentration is used to determine the concentration of an unknown solution

  
• If a 15.6 mL of a 0.120 mol/L solution of hydrochloric acid, HCl(aq), was required to titrate a 10.0mL sample of sodium hydroxide, NaOH(aq), then the concentration of the NaOH(aq) solution, expressed in scientific notation, is a.bc x 10-d mol/L.

  
• The hydronium ion concentration, [H3O+ (aq)], of a solution with a pH of 7.400, expressed in scientific notation, is a.bc x 10-d mol/L.

  
• Hydronium ion concentration


  The concentration of H3O+ ions in a solution

  
• A change in pH from 5.7 to 3.7

  Indicates a decrease in the hydronium ion concentration [H3O+(aq)] by a factor of 100
• Proton donor


  A substance that can donate a proton (H+) in a chemical reaction
• Acid deposition


  The process where acidic compounds in the atmosphere are deposited on the Earth's surface
• Reactions 2 and 7 can result in acid deposition
• Equilibrium equation


  An equation that shows the reversible reaction between reactants and products at equilibrium
• The proton donors in the equilibrium equation are CH3COOH(aq) and CH3COO-(aq)
• Comparing solutions of HCl(aq) and CH3COOH(aq) with the same concentration

  HCl(aq) has a higher hydronium ion concentration, [H3O+(aq)], and a lower pH than the CH3COOH(aq)
• pH


  A measure of the acidity or basicity of a solution

  
• If a sample of hydrochloric acid, HCl(aq), has a hydronium ion concentration, [H3O+(aq)] of 5.3 x 10-4 mol/L, then the pH of the sample is 3.28

  
• Acid solutions


  • Green
  • Yellow
  • Blue
• The student should have added an indicator to the burette in step 5 of the procedure
• Soil samples in order from greatest buffering capacity to least


  • 1
  • 2
  • 3
• Buffer


  A solution that can resist changes in pH