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CHEM 375 > Midterm 1 > Flashcards

Midterm 1 Flashcards

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1
Q

3 key research areas in environmental chemistry

A

Water security
Agriculture
Energy and mineral resources

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2
Q

Define environmental chemistry

A

chemical basis for understanding our surroundings, the global environment, with emphasis on the composition of the natural environment, the processes that take place within it, and the kinds of changes that come as a result of human activities

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3
Q

Define toxiciology

A

refers to the detrimental effects of substances on organisms at the individual level

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4
Q

Define ecotoxicology

A

refers to the effects of toxic substances on ecosystems at the population level

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5
Q

Two kinds of cycles?

A

Energy cycles - solar energy driving photosynthesis
Matter cycles - biogeochemical cycles describing the circulation of matter - elements

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6
Q

Define pollutant

A

substance present in greater than natural concentrations from human activity that has a negative impact on something in the environment

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7
Q

Difference between adsorption, absorption and sorption

A

Adsorption - one species adhering to the surface of another
Absorption - one species internally penetrating another species
Sorption - both processes together

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8
Q

Define green chemistry

A

sustainable, safe and nonpolluting practive of chemical science and manufacturing that consumes minimum amount of materials and energy while producing little or no waste

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9
Q

Define hydrosphere

A
  • freshwater and oceans
  • systems relating to and consisting of H2O - including minerals and salts found in water regions
  • 97% of planets water is found in oceans - fresh water trapped in ice
  • H2O is involved in hydrological cycling
    – atmospheric water
    – surface water
    – ground water
    – glaciers
  • sediments are considered part of the hydrosphere
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10
Q

How is lead OII adsorption affected by biocomposites?

A

agro waste biomass / biocomposite pellets adsorb a greater amount of lead II than other pellets

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11
Q

How do you calculate risk?

A

= f (hazard x exposure)

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12
Q

3 characteristics of undesirable chemicals?

A
  • persistence - DDT
  • bioaccumulation
  • toxicity - Parathion
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13
Q

What is one of the global environmental concerns?

A
  • contamination of groundwater supplies - a major outcome of industrial human activity has been the pollution of air/water
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14
Q

Difference between less developed and more developed countries?

A
  • LDC -75% of worlds population - 90% of population growth
  • DC -20% of world population - but consume 70-80% of world resources and energy
  • DC most concerned with long term effects of the impact of industrial pollution on the environment of developed countries - hazardous / nuclear wastes, acid rain, smog

LDC most concerned with food supply, fuel, deforestation, drought and food security

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15
Q

Define atmosphere

A

thin layer of gas surrounding the planet
- moderates temperature, absorbs energy, which is then transferred from quatorial regions
- medium of transport of water and other important substances
- examples of regions - troposphere, stratosphere etc
- contains gravity captured gasses from space - N2 and O2
- minor amounts of CO2 and H2O

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16
Q

Define hydrosphere

A
  • freshwater and oceans
  • systems relating to and consisting of H2O - including minerals and salts found in water regions
  • 97% of planets water is found in oceans - fresh water trapped in ice
  • H2O is involved in hydrological cycling
    – atmospheric water
    – surface water
    – ground water
    – glaciers
  • sediments are considered part of the hydrosphere
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17
Q

5 environmental components - spheres

A
  • Atmosphere
  • hydrosphere
  • geosphere
  • biosphere
  • anthrosphere
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18
Q

2 processes transferring substances between environmental compartments

A
  • flux - amount of material transferring between compartments
  • burden - masses of material in each compartment
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19
Q

cellulose and starch have what kind of glycosidic linkages?

A

cellulose - B1-4 glycosisdic linkages
starch - a1-4 glycosisdic linkages

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20
Q

explain the two kinds of biogeochemical cycles

A

Exogenic cycles
- occur on surface
- mainly atmosphere, but involve other compartments as well

Endogenic cycles
- involves subsurface rocks

  • soil and sediment are the interface between the two
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21
Q

Which element only cycles in endogenic cycles, not exogenic - (no atmosphere)

A
  • phosphorus only circles in the ground
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22
Q

Define geosphere

A

Inorganic component of the environment
- usually called the lithosphere, consists of the upper mantle and crust of the Earth
- part of the geosphere directly involved with environmental processes and in contact with the other compartments

  • primarily consists of rock - soil, crust, volcanoes
  • rock is made of minerals which are naturally occuring inorganic solids with definite crystal structure and chemical composition
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23
Q

Define biosphere

A

consists of all life forms and the components necessary for their formation
- strong interactions between biotic and abiotic portions - biogeochemical cycles
- biomass crucial for life comes from biosphere

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24
Q

Define anthrosphere

A

Can be reffered to a the sum of human activities and processes
- a seperate compartment similar to the biosphere and part of it
- environment made of modified by humans and used for their activities
- technology and its effects
- substances are removed from the abiotic environment , transformed, stored, used and eventually returned to the environment
- comprised of cities towns, fields, industry, machines, transportation

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25
Define ecosystem
A group of organisms and their environment which are interrelated and dependent on eachother - a system including the interaction of both abiotic and biotic componenets within a defined area
26
Define contaminant
Causes a change in the normal concentration of an environment but does no damage - contamination can occur in any of the regions of the environment - can be naturally occuring
27
Define pollutant
A contaminant that causes damage as a result of human activities - Source - where the pollutant originates - Receptor - anything affected by the pollutant - Sink - long term depository of a pollutant ---- limetone can be considered a sink for atmosphere sulfuric acid through a chemical reaction
28
Define xenobiotic compound
Matter not normally part of an organisms environment. if the compound causes damage, then it is a poison or toxic contaminant - can be found in any region
29
4 types of intermolecular forces weakest to strongest
London dispersion forces - all molecules and atoms Dipole dipole - polar molecules only Hydrogen bonding - molecules w/ H bonded to F O N Ion- dipole - mix of ionic and polar compounds
30
Various important properties of water?
Excellent solvent Forms H bonds high boiling point expands on freezing transparent high thermal stability high heat capacity
31
3 types of water stores
Surface water - streams lakes estuaries Wetlands - shallow flooded areas Estuaries - arms of the oceans into which streams flow - food source and habitat for many organisms
32
What are the upper and lower layers of a water body called + transition region
Upper - epilimnion Lower - hypolimnion Transition - thermocline - the two layers generally do not mix especially in larger bodies - overturn / mixing occurs seasonally - top is warmest in summer and bottom is warmest in winter - difference in density with temperature mix during fall / spring
33
What is eutrophication in an aquatic environment?
caused by excess productivity - decay or excess biomass or the overconsumption on oxygen
34
5 main physical factors affecting aquatic life
- temperatuure - transparency - turbulence - dissolved oxygen in water - biochemical oxygen demand - BOD from degradable substances
35
Different layers of a water body depending on exygen content
oxic - surface - oxygen rich - oxidizing layer anoxic - bottom - oxygen poor - reducing layer
36
What are the two main gasses dissolved inw ater
O2 - for fish CO2 for algae - accorrding to henrys lay the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas in contact with the liquid
37
What is Henrys law?
- gases partition betweenn atmosphere and water - goverened by partial pressure of the gas in atmosphere - Kh = X solv / X gas - as pressure increases so will the amount of gas dissolved in the water - constant = Xsolv / Pressure (X(g)
38
How do the dissolved solids in natural waters differ from river to ocean?
Concentration of ions is much greater in the ocean than in the river enviroinment
39
Define alkalinity
the capacity of water to accept H+ ions
40
THree sources of alkalinity?
HCO3-, CO32-, OH-
41
Can we use pH to measure alkalinity?
- not really - weal carbonate bases more abundant than OH- - many natural waters are not in equilibrium with the atmosphere
42
Two ways to measure alkalinity?
phenolphtalein alkalinity - CO32- + H+ ----- HCO3- - strong buffering capacity total alkalinity - Carbonate with hydrogen to CO2 - bicarbonate with hydrogen to CO2
43
What is water hardness?
Addition of di and trivalent cations to water - generally Ca2+ and Mg2+ or alkaline earth elements
44
What type of rock gives hardness and alkalinity and what type of rock only gives hardness?
Limestone - CaCO3 ---> Ca2+ + HCO3- + CO23- hard and alkaline Gypsum - CaSO4 ---> Ca2+ + SO42- hard only because SO4 2- is very weakly basic
45
Is there a difference in composition in surface water vs ground water?
yes - clder temp underground gives higher CO2 solubility in ground water due to henrys law constant - partial pressure underground is also greater than at sea level - as partial pressure raises so does solubility - temporary hardness can be removed by heating - precipitating CaCO3 - part of the Ca will leave as H2O/CO2 - driving off CO2 when biolinh leads to EQ shifting to the right - resulting in scale in hot water pipes
46
What is soft water?
Water with low concentrations of Ca and Mg and low concentrations of anions - therefore has a lower alkalinity - usually in areas with igneous / granite rock - much less leaching and lower concentrations of HCO3- -however low alkalinity results in less buffering capacity as carb and bicarb are great buffers - results in more damage from an influx in acid - acid mine leaching - some bacteria release H+ as well during decomposition processes
47
What are zeolites?
common kinds of cation exchangers - porous sand like materials with cation exchange sites SiO2 and AlO4 units - Al in the zeolites provides the exchange site and the polymer provides the support for the zeolites
48
Two issues to deal with regarding apparent high concentrations of CaCO3 in seawater
ionic strength and complexation
49
What is activity?
COncentration under ideal conditions - activity is equal to concentration under ideal conditions and the activity coefficient is 1, under high concentrations that value can differ from 1 - in seawater gamma = 0.26 for Ca2+ and 0.20 for CO32- -therefore the Qsp =activity(Ca2+) x activity(CO32-
50
Are charged ion complexes likely more soluble than non charged ones?
Yes due to the charge and waters permanent dipole - will be very soluble in water
51
Define complexation in the case of metal ions
- complexation occurs with the metal ion bound to one or more ligands (like H2O or NH3) as illustrated by the equilibrium - the ligand is a neutral molecule or ion that acts as a lewis base with the metal which acts as a lewis acid - Fe2+ + 6NH3 <---> Fe(NH3)6 2+ - oxygen / carbon monoxide binding to hemoglobin is an example of complexation - equilibrium can be defined by a formation constant (kf)
52
Two kinds of ligands
Unidentate - a ligand with one binding site - amine, carboxylate ions Multidentate - a ligand with 2 or more binding sites - also known as a chelating agent - EDTA, NTA, phosphates
53
What are end of pipe and closed loop industrial processes?
End of pipe - pollutants and wastes are controlled after they are produced Closed loop - pollutants are recycled or integrated with the environment - effectively zero emissions
54
3 important properties of water and why they are significant
Universal solvent - great at transferring nutrients and waste products enabling biological processes to occur in an aqueous medium Transparent to visible and long wave light - allows light required for photosynthesis to reach considerable depths in bodies of water Maximum density as a liquid at 4deg C - means ice will float and vertical circulation is restricted in stratified water
55
4 main reactions in water chemistry
acid base -> CO3 2- + H2O -> HCO3- + OH- complex formation redox NH4+ -> NO3- precipitation Ca2+ + CO3 2- --> CaCO3
56
Gas solubility _____ as temperature increases
decreases
57
What is the formula for calculating alkalinity?
alk = HCO3- + 2CO3 2- + OH- - H+
58
Two ways to soften water?
Lime and Soda ash Ion exchanger with negative ion exchange sites
59
Complexation example
Fe2+ + 6NH3 (ligand lewis base) ---- Fe(NH3)6 2+
60
complexation vs chelation
complexation is a ligand binding to a metal ion chelation occurs with chelating agents that can bind in more than one place - multidentate ligand
61
What does pE say about the environment?
large positive = oxidizing environment - compound attracts electrons negative = reducing envirionment - compound gives up electrons
62
What is corrosion
destructive alteration of metal through interactions with its surroundings M --- M2+ + 2e-
63

CHEM 375 (4 decks)

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