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Abiotic Factors - Chemistry

Abiotic Factors - Chemistry. Chemical make-up of Seawater. Special Properties - due to H-bonding, polarity 1. high heat of fusion (335 J g -1 ) - only NH 4 is higher 2. high heat of vaporization (44 kJ mol -1 at 24 o C) 3. high specific heat (4.18 J g -1 o C -1 )

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Abiotic Factors - Chemistry

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  1. Abiotic Factors - Chemistry

  2. Chemical make-up of Seawater Special Properties - due to H-bonding, polarity 1. high heat of fusion (335 J g-1) - only NH4 is higher 2. high heat of vaporization (44 kJ mol-1 at 24oC) 3. high specific heat (4.18 J g-1oC-1) 4. adhesion & cohesion a. surface tension b. capillary action

  3. Seawater has many salts. What does this do to the characteristics of water? Why? 1. osmotic pressure raises 2. boiling point raises 3. density increases 4. electrical conductance increases 5. vapor pressure lowers 6. freezing point is depressed

  4. Other “Salty” Facts You Ought to know • A kilogram of average seawater contains 34.7 g of salts = expressed as 34.7 ppt (gm kg-1, o/oo) • Can also be measured as conductivity relative to KCl at 15oC at 1 atm pressure. • Ranges 1. oceanic = 32-38 ppt 2. hypersaline > 38 ppt 3. estuarine =1-32

  5. Biotic Classifications based on salt tolerance 1. euryhaline or euhaline = 30-40 ppt 2. polyhaline = 18-30 ppt 3. mesohaline = 3-18 4. oligohaline = 0.5-5 ppt 5. brackish = 5-10 ppt (varies by author)

  6. Salinity measurement 1. density: hydrometer & pycnometer 2. resistance to elect. current: conductivity meter or salinometer 3. bending of light from air to saltwater: refractometer 5. chemical: determination of [Cl] through titration with AgNO3 = chlorinity AgNO3 + NaCl <-> AgCl ( ppt ) + NaNO3

  7. Oxygen in seawater • [O2] ~ 0.9% in seawater vs. 21% in atmosphere • Sources: atmosphere & net photosynthesis Photosynthesis ---------> 6 CO2 + 6 H2O <--> C6H12O6 + 6O2 <------------ Respiration

  8. Determination of O2 in Seawater DO Meter 1. polarographic probe, Au+ , Ag- 2. O2 diffuses through a thin membrane, generating a current between + & - proportional to [DO] in water 3. O2 is used up at the surface of the probe, so it needs to be stirred to give accurate readings

  9. DO measurement => Winkler titration 1. sample taken in BOD bottle 2. dissolved oxygen in sample converted to a brown ppt. MnSO4 + 2KOH --> K2SO4 + Mn(OH)2 2MN(OH)2 + O2 --> 2MNO(OH)2 (ppt ) 3. sample is acidified to liberate I2 MnO(OH)2 + 2H2SO4 --> 3 H2O + MN(SO4)2 Mn(SO4)2 + 2KI --> MnSO4 + K2SO4 + I2 4. iodine removed by titration with Na2S2O3 2 Na2S2O3 + I2 --> Na2S4O6 + 2NaI 5. end point is reached with a starch indicator solution becomes colorless

  10. Constituents of Seawater: CO2 most important factor in controlling pH Buffer!!!! = resists change in pH CO2 + H2O <-> H2CO3 <--> H+ + HCO3- <-> 2H+ + CO3-2 Carbonic AcidBicarbonateCarbonate CO2+ H2O+CO3-2 <-> 2HCO3-

  11. CO2 facts • ~99% in seawater as bicarbonate or carbonate • during photosynthesis, • a. CO2 is removed • b. HCO3- is converted to H2CO3 then to CO2 • c. H+ used • d. pH  • e. respiration reverses process • f. O2 production or CO2 removal can be used to measure photosynthesis

  12. calcification • how shells, corals and coraline algae get their raw material Ca+2 + 2HCO3- <-> Ca(HCO3)2 <-> bicarbonate calcium bicarbonate CaCO3 + H2CO3 calcium carbonate carbonic acid

  13. Nutrients shown essential for plant growth --> CHOPKNSCaFe, Mighty good, but Not always Clean. CuMnCoZnMoBy

  14. How do we know these elements are essential? • Constituent analysis: grind and find out of what the tissues are made • Growth studies: deprive and look for deficiency symptoms, stunted growth or death.

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