Exam 1- Soil Chem

Front 1

Open system

Back 1

A system thatfreely exchanges matter and energy with the surroundings.

Front 2

Heterogeneous system

Back 2

Multi-phase and multi-component system.

Front 3

What are the five most prevalent elements in crustal rock and soil?

Back 3

O, Si, Al, Ca, Fe

Front 4

What are the dominant forms of the two most prevalent elements in soil?

Back 4

Si, O

Front 5

Which two elementsare most enriched in soil relative to crustal rock?

Back 5

C, N

Front 6

electronegativity

Back 6

A measure of the tendency for an atom to attract a bonding pair ofelectrons.

Front 7

covalent bond

Back 7

A chemical bond that involves thesharing of electrons between atoms.

Front 8

ionic bond

Back 8

A chemical bond formed between two ions of opposite charge.

Front 9

H-bond

Back 9

An attractive force between the hydrogen attached to an electronegativeatom of one molecule and the electronegative atom of a different molecule.

Front 10

van der Waals interactions

Back 10

Induced electrical interactionsbetween molecules or atoms that are close to each other.

Front 11

Primary mineral

Back 11

Inherited from parent material.

Front 12

secondary mineral

Back 12

Products of primary mineralweathering.

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weathering

Back 13

The breaking down on rocks, soil and minerals under influence of environmental drivers.

Front 14

physical weathering

Back 14

Breaking apart of rock to decrease particle size and interfacial area(ie: freeze thaw and erosion).

Front 15

chemical weathering

Back 15

Changes in the molecular structure of minerals with effects on surface area, composition, and particle size.

Front 16

incongruent weathering

Back 16

Weathering that results in formation of secondary minerals.

Front 17

phyllosilicate clay

Back 17

Secondary aluminosilicate minerals with regular layer structure.

Front 18

isomorphic substitution

Back 18

The replacement of one structural ion by another of equal or differentcharge, without a change in structure.

Front 19

tetrahedral layer

Back 19

a plane composed of a cation (usually silicon) bonded to 4 anions (usually oxygen) that form a sheet whose CN is 4.

Front 20

octahedral layer

Back 20

a plane composed of a cation (usually Al or Mg) bonded to 6 anions (usually oxygen) that form a sheet whose CN is 6.

Front 21

dioctahedral

Back 21

There are 3 possible positions for a cation in an octahedral sheet. If 2/3 of the positions are occupied, it is dioctahedral. The cations must be trivalent to maintain neutral charge.

Front 22

trioctahedral

Back 22

There are 3 possible positions for a cation in an octahedral sheet. If 3/3 of the positions are occupies, it is trioctahedral. The cations must be divalent to maintain neutral charge.

Front 23

permanent charge in phyllosilicate clay

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Constant charge deriving from isomorphic substitution in a crystallinestructure.

Front 24

pH-dependent (variable) charge

Back 24

Derives from proton (H+)adsorption and desorption on surface hydroxyl groups.

Front 25

cation exchange capacity (CEC)

Back 25

Maximum adsorption of readilyexchangeable cations on soil particle surfaces.

Front 26

What is the mostcommon cation found in tetrahedral coordination?

Back 26

Si4+

Front 27

What is the most common cation found in octahedral coordination indioctahedral minerals?

Back 27

Al3+

Front 28

What is the most common experimental technique used to identify clayminerals in soils?

Back 28

X-ray diffraction

Front 29

What clay minerals contribute to shrink-swell phenomenon in soils?

Back 29

vermiculite and smectite

Front 30

Rank in the order the CEC of kaolinite, vermiculite and montmorillonitefrom lowest to highest.

Back 30

L: kaolinite

montmorillonite

H: vermiculite

Front 31

What units can be used to express CEC?

Back 31

molc/kg

Front 32

global carbon pools

Back 32

A reservoir with the capacity to store and release carbon.

Front 33

soil organic matter (SOM)

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- Organic residues, humus, soil biomass, biomolecules, humic substances. Can be dissolved in soil solution, discrete solid phase organic colloids and aggregates, complexed with soil minerals or a constituent of soil gas phase.

Front 34

soil carbon pools

Back 34

Organic residues, humus, soil biomass, biomolecules, humic substances.

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recalcitrance

Back 35

Resistance to degradation.

Front 36

lignin

Back 36

A very stable component of cell walls that protects cells from attack bymicroorganisms and is not easily degraded.

Front 37

pKa value

Back 37

Acid dissociation constant. Proton dissociation (negative charge)increases with decreasing H+.

Front 38

· Flux of atmosphericcarbon to terrestrial biota is due to what chemical process?

Back 38

Photosynthesis.

Front 39

Flux of carbon from the soil to the atmosphere is due to what chemical reaction?

Back 39

respiration

Front 40

List the 3 majortypes of carbon-containing structures in mature plant materials.

Back 40

cellulose, hemicellulose and lignin.

Front 41

Name and discuss in detail the three principal mechanisms responsiblefor “stabilizing” organic matter against oxidative degradation in soil.

Back 41

Recalcitrance, inaccessibility, and interactions.

Front 42

Supramolecular humic model

Back 42

Aggregatethrough intermolecular forces.

Front 43

Macromolecular humic model

Back 43

Phenolic aldehydes and acids are altered to quinones that may polymerizewith amino compounds to form humic macromolecules.