Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

geog 305 > Sesquioxides and Ion Exchange > Flashcards

Sesquioxides and Ion Exchange Flashcards

1
Q

what are Fe and Al oxides and hydroxides (sesquioxides)?

A

weathering products of clay minerals that have lost all Si ions and other cations except Fe 3+ and Al 3+ -> consist of modified octahedral sheets of Fe3+ and Al3+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are three characteristics of Fe and Al sesquioxides?

A
  • little to no isomorphous substitution
  • little cation exchange capacity
  • posses covalent bound OH- ions which may cause strong absorption of certain anions like phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are 5 Fe and Al sesquioxides and their color?

A
  1. goethite Fe(OH)3 - brown
  2. limonite Fe(OH)3- yellow
  3. haematite Fe2O3- red
  4. gibbsite Al(OH)3- colourless
  5. alumina Al2O3- colourless
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do dark colors signify in soil?

A

high organic matter content

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does red signify in soil?

A

soil rich in iron oxides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does blue-grey color signify in soil?

A

presence of iron in its reduced form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why does soil become blue/grey?

A

with prolonged water saturation, iron oxides are loss and aluminum oxides and hydroxides dominate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is laterite?

A

cementation in soil when large oxide or hydroxide content -> tropics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

which particles types of minerals provide anion exchange capacity?

A

sesquioxides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the three sources of negative charges for cation exchange capacity?

A
  1. isomorphous substitution within clay minerals
  2. broken bonds at edge of clay minerals
  3. dissociation of bonds at edge of humus (carboxylic or phenolic)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how do you compare primary and secondary minerals to a pile of books?

A

primary minerals: book covers
secondary minerals: pages of book

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how does soil solution become acidic?

A

exchange of base cations by hydrogen until there are no more base cations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why is prolonged soil acidification worrisome?

A

because strong Al bonds may eventually break and leach into soil solution which is toxic to plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how can acidification of soil be reversed?

A

through fertilization (Ca, K) or nutrient release from decomposing tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the process of adding calcium or magnesium to soil called?

A

liming ! adding base cations to soil to decrease acidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are three mechanisms of neutralization of acid rain?

A
  • reaction with carbonates (Ca binds to sulfate)
  • reaction with exchangeable cations or weatherable minerals such as feldspar (Cation binds to sulfate)
  • anion adsorption of SO4 of Fe and Al hydroxides
17
Q

why can soils rich in Fe and Al neutralize acid rain?

A

through anion adsorption

18
Q

what solution is best for soil that has been affected by acidic rain?

A

calcium carbonate because adding calcium chloride would not help the problem long term. as soon as it would acid rain again, the equation would reverse. Calcium carbonate is irreversible!

19
Q

how do you determine how tightly a cation will be bound to the surface of a colloid?

A

the higher the charge and the smaller the hydrated radius of the cation, the more strongly it will adsorb to the colloid
- ALSO likelihood that an adsorbed cation will be displaced is influenced by how strongly its neighboring cations are adsorbed

20
Q

what cation has the strongest adsorbtion?

A

aluminum 3+, once it is mobilized, soil no longer has any buffering capacity

21
Q

how are cations measured?

A

cations per mass of soil

22
Q

how do you calculate cation exchange capacity?

A

total amount of charges per soil which is found by first finding moles per soil

23
Q

why do kaolinites have low CEC?

A

because of the strong hydrogen bonds between sheets

24
Q

what mineral has good CEC?

A

smectites!

25
Q

what is the relationship between SOC and CEC?

A

the higher the SOC, the larger the CEC

26
Q

what is the relationship between pH and CEC?

A

the lower the pH, the lower the cation exchange capacity because cations have already been exchanged in acidic soils

27
Q

how does anion exchange capacity work?

A

anions and organic matter displace OH- groups from sesquioxides

28
Q

why do we have to add a lot of P to tropical soils?

A

phosphate bonds strongly to iron/al oxides in soil, making it unavailable to plants

29
Q

what is the relationship between pH and surface charge?

A

the higher the soil pH, the larger the negative charge

geog 305 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions