Geochemistry Exam 3

karst

A special type of aquifer with very large pore spaces.

CO2 + H2O > H2CO3; H2CO3 > H+ + HCO3-; 2 H+ + CaCO3 > CO2 + Ca2+ + H2O

What are the three steps in the dissolution of limestone?

more

Smaller grain sizes are ____ soluble because of higher surface area.

fabric porosity

Primary porosity from diagenesis

secondary porosity

permeability

bed thickness, structure, stratigraphy

What are the three parts of geology that need to be considered to understand cave formation?

precipitation/dissolution

What part of water chemistry needs to be considered to understand cave formation?

rates of water flow; permeability models

What part of hydrology needs to be considered to understand cave formation?

CO2, H2CO3*, HCO3-, and CO3(2-)

DIC is the sum of..?

-6.35

What is the value of K1 on the carbonate bjerrum plot?

-10.33

What is the value of K2 on the carbonate bjerrum plot?

acid mine drainage

Generates SO4 from the oxidation of pyrite. 

CO2 + H2O > H2CO3*

What is the equation that get gas into water to make acid?

H2CO3* > H+ + HCO3-

What is the equation for the first dissociation constant of carbonic acid?

HCO3- > H+ + CO3(2-)

What is the equation for the second dissociation constant of carbonic acid?

H2O > H+ + OH-

What is the equation for the dissociation constant of water?

CaCO3 > Ca(2+) + CO3(2-)

What is the equation for acid dissolving calcium carbonate?

saturation index

The numerical representation of saturation; what is measured in solution vs what we expect to be there

positive

If IAP > Ksp, SI is..?

negative

If IA{ < Ksp, SI is..?

dissolvable rock and a weak acid

What are the two things needed to form a cave?

Eh

What is the variable used to understand redox?

Movement of e- from one species to another.

What is redox about?

oxidation

Losing electrons

reduction

Gaining electrons

0

What is the oxidation state for elemental forms or monatomic gases?

0

Neutral compounds must have oxidation states of?

equal

All oxidation states of a ion must _____ the charge of the ion.

+1

Oxidation state?: group 1 metals (K, Na)

+2

Oxidation state?: group 2 metals (Ca, Mg)

-2

Oxidation state?: oxygen

+1

Oxidation state?: hydrogen

-1

Oxidation state?: fluorine

-1

Oxidation state?: chlorine

energy

Redox reactions always produce..?

terminal electron acceptor

The breakdown of organic carbon (or the oxidation of reduced carbon) requires a..?

Oxidation potential; electrical energy associated with e- transfer

What is Eh?

higher

Eh ______ = oxidizing

lower

Eh ______ = reducing

oxidizing

Mining is taking reduced things and placing them in an __________ environment.

pyrite

When ______ (reduced Fe) is introduced to oxygen it dissolves and Fe is oxidized.

biological

Terminal electron acceptors control ________ redox.

sulfides

Swamps and wetlands are low oxygen environments (reduced settings) that form..?

ombrogenous bogs

Depend on rain for their formation; low pH, 3.5-4.5; sphagnum species

topogenous bogs

High water table, gw to exist; poorly drained; nautral-alkaline pH

dissolved organic carbon

Water-soluble source of carbon that constitutes the largest pool of organic matter in freshwater systems. 

humic substances

Large macromolecules from diagenesis and decay of organic matter

kerogen

Sedimentary organic matter, generally insoluble, heating breaks down into different groups of hydrocarbons

Van Krevelen plot

Organic substances in geologic record (kerogen, liquid hydrocarbons, gaseous hydrocarbons, coal)

aliphatic

Chain or branch compounds

aromatic

Ring structure delocalized electron clouds

functional groups

Small groups attached to molecules; control the function of the molecules

H/C ratio

Relative indicator of proportion of aliphatic to aromatic.

More aliphatic

Higher H/C ratio = ?

more aromatic

Lower H/C ratio = ?

petroleum

Made of dead algae and plankton; settles in reducing environment; lithifies into black shale; rising temperature converts organic matter into kerogen

organic matter, kerogen, tar, oil, gas

Rank the forms that petroleum take from low to high temperatures

crude oil

Complex mixture; separated by distillation (BP); paraffin and cyclic ring

natural gas

Lightweight alkanes; methane and ethane sold as gas; propane and butane are liquified natural gas

distillation

Separate crude into product by boiling point.

smaller

In distillation, _______ compounds boil/melt at a lower temperature.

volatility

Ability of compound to escape into gas form from a condensed phase (boiling). 

Mass, overall size, length, surface area

What about the size of compounds impacts their volatility?

polarity, acid-base properties, H-bond

What about the intermolecular attractions of compounds impacts their volatility?

aqueous solubility

Maximum concentration of a compound that can dissolve in water

polarity and size of compound

What two factors impact solubility?

LNAPLs

light nonaqueous phase liquids; float on water

DNAPLs

dense nonaqueous phase liquid; sink in water

light and dense non aqueous phase liquids

What compounds cause concern due to their mobility in aquifers?