E-chem Exam

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Author:
anime1003
ID:
239926
Filename:
E-chem Exam
Updated:
2013-10-10 13:24:54
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Midterm
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Description:
Solubility, smog, ph
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  1. Equilibrium Constant expression
    aW+bX->cY+dZ

    K=[Y]c[Z]d/[W]a[X]b
  2. Types of equations for solving multiple Equilibria
    • Equilibrium-constant equations
    • Mass-balance equations
    • –Relate
    • equilibrium concentrations of species with the analytical concentration of
    • solutes

    • Charge-balance equations
    • –Based
    • on idea that electrolyte solutions have to be electrically neutral
  3. Charge balance equations
    • # moles positive charge/L = # mols negative charge/L

    •  Remember that the # mol gets multiplied by charge to give the moles of charge, e.g., for 0.20 mol Mg2+, there are 0.40 mol of positive charge.
  4. Steps for solving mutiple equilibria
    • 1)Write balanced chemical equations for all
    • relevant equilibria
    • 2)State in terms of equilibrium conc. the
    • variable being sought
    • 3)Write equilibrium constant expressions
    • for all the equilibria and find the appropriate K values
    • 4)Write mass balance expressions
    • 5)Write any available charge-balance
    • expressions
    • 6)Make sure # of unknowns equals # of
    • equations.  If not, try to approximate
    • concentrations of some of the unknowns
    • 7)Approximate as possible to simplify the algebra
    • 8)Solve the equations
    • 9)Check validity of approximations
  5. Solving ph for a buffer
    • HA + H2O = H3O+ + A-  

    • Na+ + A- + H2O=OH- + HA + Na+          
  6. Ka
    [H3O+][A-]/[HA]
  7. Kb
    [OH-][HA]/[A-]
  8. Assumptions for buffers
    • 1.if Ka or Kb
    • is >10-3 (strong acid or base)

    • 2. if the molar concentrations of HA or A- are very small so that the assumptions
    • that we can ignore [OH-]
    • and/or [H3O+]
    • no longer hold.
  9. Alkalinity
    comes from charge balance.  

    # negatively charged species = # positively charged species
  10. 4 major groups of clay
    • Kolinite
    • illite
    • chlorite
    • montmorillonite
  11. Kaolinite
    product of intense tropical and desert weathering. Most found in equatorial sediments. Note lack of exchangeable cations…
  12. Chlorite
    • polar sources
    • physical weathering 
    • lots of exchangeable ions
  13. Illite
    • one of the most common clays.
    • High in potassium
    • Land-derived, in oceans highest in concentration in midlatitudes in the northern hemisphere (which has more land)
  14. Montmorillonite
    • expanding clay
    • weathering in poor drainage areas
    • in situ weathering product of volcanic ash
  15. Soap
    potassium or sodium salt of a fatty acid
  16. detergent
    acts to reduce interfacial or surface tension
  17. Partial Pressure
    X=PCO2/Ptotal
  18. Biological pump of carbon
    life such as plants that use photosynthesis to creat organic carbons form the atmosphere
  19. Physical ocean pump
    oceans take up 2.2Gt/yr of carbon due to solubiliy
  20. Solubility Product
    Ksp=[X]a[Y]b= XY in molarity
  21. Why organic matter is important
    –Building blocks for life/energy source for heterotrophs

    –Global C cycle

    –O2 balance

    –Climate

    • –Affects
    • contaminant transport

    • –Affects
    • nutrient transport

    • –Affects
    • light penetration
  22. DOM
    Dissolved organic matter
  23. POM
    Particulate organic matter
  24. Humic Matter
    -leftovers of biologically-produced material

    -Heterogeneous

    -Biologically refractory

    -Involved in photochemical reactions

    -Form complexes with metals

    -Involved in hydrophobic interactions with anthropogenic organic compounds

    -Form disinfection by-products during drinking water treatment

    -Affect soil fertility, also weathering processes
  25. Humic Acid
    • soluble in alkaline solutions, insoluble
    • below pH 1 (I have also seen pH 2 used as criterion)
  26. Fluvic Acid
    • alkaline extractable, soluble over whole
    • pH range
  27. Humin
    Insoluble in acid or base
  28. Humic substance charatceristics
    • - have aromatic character, phenolic OH
    • groups, carboxylic groups, aliphatic OH groups
    • -yellow or brown color
  29. why [H+]2
    H+=Aas long as the dissosciation of HA is the main source of H+ ion and not water
  30. Kw=KaKb=10-14
    Kw=[H+][OH-]
  31. [HCO3]=
    =Ka(CHA/CNaA)

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