EAES 230: Earth Materials, EXAM #1, Taken from Dr. Nagy's Lecture Notes, Lecture 5: Types of Bonds, non-silicate mineral groups, Lecture 09/10 Review of bonds at mineral surfaces, and Lecture 09/12 WATER, A LIQUID EARTH MATERIAL

ionic (electrostatic)

NaCl exhibits _________________ bonding

covalent

CH4 exhibits ___________ bonding

transitional bond

part ionic & part covalent (also sometime called "Hybrid" bond.
(e.g. NaCl bonding is really 71% ionic and 29% covalent)

electronegativity

Amount of ionic vs. covalent character depends on the difference in _________ of the two elements.
En(Na) = 0.93
En(Cl) = 3.16
3.16 - 0.93 = 2.23
*The bigger the difference, the more ionic the bond.*

van der Waals force

the set of attractive or repulsive forces b/w molecules (or b/w parts of the same molecule) other than those from covalent or ionic bonds

asymmetrically

Why do van der Waals force(s) exist?
electrons are distributed ___________________ in the electron cloud at any one point in time. So, weak electric dipoles exist over a molecule. Some areas will have higher positive charge and other areas higher negative charge, at any one instant.
The positions of the areas fluctuate rapidly. The charged areas attract oppositely-charged regions on other molecules.

hydrogen bond

the __________________ is stronger than most other van der Waals interactions, but weaker than covalent or ionic bonds.

covalent; hydrogen

the bonds b/w H and O in the water molecule are mostly ______________.
The bonds b/w any two H2O molecules are ________________ bonds

hydrophobic "bonding"

is relatively stronger than a hydrogen bond.

hydrophobes

"low water soluble" molecules. They are nonpolar molecules and, if organic, usually have a long chain of carbons that do not interact with water molecules

covalent; ionic

____________ bonds are usually stronger than ___________ bonds, but the opposite can be true depending on the molecule

intermolecular (van der Waals forces or hydrogen bonds) forces

Covalent and ionic bonds will always be stronger than ____________________ in any given material

isodesmic

EV < 1/2 [Z] of anion: In halite, NaCl, Na is surrounded by 6 chloride ions and its EV = 1/6, AND, all Na-Cl bonds have the same EV

anisodesmic

EV > 1/2 [Z] of anion: the anion gives up more negative charge to the cation inside the polyhedron than to other cations outside the polyhedron (e.g., carbonates, phosphates, sulfates).

mesodesmic

EV = 1/2 [Z] of anion: (e.g., quartz) In SiO4, EV = 4/4=1, leaving O with -1 charge not shared. Since 1 = 1/2 the [charge] of O2-, the oxygens bonded to Si inside the polyhedron can be just as tightly bonded to cations outside.

anions; anionic

most minerals are classified chemically based on their _______ or ________ polyhedral groups.

Exceptions are native elements, which have metallic bonds (e.g., copper and silver)

Halides: F-, Cl-, Br-

Bonds that are largely ionic in character (e.g., fluorite CaF2 and halite NaCl)

Sulfides: S-, S2-

ionic and covalent bonds (e.g., pyrite FeS2, Troilite FeS, Cinnabar HgS)

hydroxides

OH- (covalent)

oxides

O2-

oxyhydroxides

O2- and OH- (covalent)

carbonates

(CO3)2- (e.g., calcium carbonate CaCO3 and dolomite (Mg,Ca)CO3

trigonal planar

carbonate anionic units ((CO3)2-) are ________________. Their oxygens are shared with octahedra whose center cation is calcium. (e.g., calcite)

Phosphates

(PO4)3-

sulfate

(SO4)2-

tungstate

(WO4)2-

sheet (phyllo) silicates

Rings of Si Tetrahedra. Stacked sheets of tetrahedra linked rings attached to sheets of octahedra linked rings. (e.g., muscovite - mica and kaolinite - clay)

TO

kaolinite is a "____" clay

gypsum, muscovite, talc, graphite, kaolinite

Minerals with one prominent cleavage direction

kaolinite

Al2Si2O5(OH)4

carbon dioxide

is an important weak acid in natural waters

dissolving; precipitating

minerals can change water pH by ________________ into the water or _____________ from the water

mineral surfaces

___________ can act as acids or bases without dissolving

organic matter

dissolved ________________ can act as an acid or base.

amphoteric

water is both an acid and a base: it is "____________"

[H+]

pH goes down as _____ increases in water.

the equilibrium constant

Kw = [H+][OH-] = 10^(-14)
[ ] = concentration or "activity"
also,
Kw = [H+][H+] = [H+]^2

completely

strong acids and bases: _________________ break down in water

partially

weak acids and bases: ___________________ break down in water

2.5-4

Acid rain has a pH of ~__________.

6-7

typical streams have a pH of ________.

6-8

Lake Michigan pH varies from ________.

8.07

the ocean has an average pH of ~______.

9.3

Salt lakes have a pH of ~_____.

polar

water molecules are ___________. water is the "universal solvent".

decreasing

the pH of the ocean is ________________.

8.179; 0%

Pre-industrial (18th century):
pH: ___________
H+ concentration change relative to pre-industrial: ____________

8.104; +18.9%

recent past (1990s):
pH: ___________
H+ concentration change relative to pre-industrial: ____________

8.07; +28.8%

present levels (today: 407 ppm CO2):
pH: ~___________
H+ concentration change relative to pre-industrial: ____________

7.949; +69.8%

2050 (est. at 560 ppm CO2):
pH: ___________
H+ concentration change relative to pre-industrial: ____________

7.824; +126.5%

2100:
pH: ___________
H+ concentration change relative to pre-industrial: ____________

carbonic acid

CO2 dissolves in ocean water to make _________________ which converts to carbonate that organisms use to make their carbonate mineral shells (mostly calcite).

mineral solubility

________________________ regulates the pH. The amount of dissolved (CO3)2- in equilibrium with carbonate minerals limits the amount of H+ in seawater.

hydrolyze

cations that "____________" in water can change pH.

hydration shell

small ions with high charge tend to hold onto some water molecules.
(e.g., Fe3+ tends to hold onto 6 water molecules)

hydrolysis reaction

Fe3+ in water can split a water molecule into a cation (H+) and an anion (OH-), keeping the OH- and releasing the H+

Natural organic matter (NOM)

both a source of and a sink for protons (H+) in natural water.
(e.g., cache river wetlands, southern illinois. cyprus trees as old as 200 years. organic-rich swamp or "black" water can have pH of around 4.4)

bulk minerals

are electrically neutral, but their surfaces can have atoms whose charge is not fully neutralized (or, "satisfied").

(e.g., on quartz, the exposed O and/or Si atoms combine with protons or hydroxyls in the water to make surface groups of atoms: >SiOH

NaHCO3; Na2CO3

_______(nahcolite) and _______(thermonatrite) precipitate in hojt springs, salt lakes, shallow evaporating ocean water, and volcanic fumaroles.
(e.g., baking soda, baking powder, ramen)