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SOIL 2124 EXAM 3 Questions and Correct
Answers/ Latest Update / Already Graded
mineral or organic particles in soil having a diameter less than 1um
(0.000001 m)- CLAY SIZE RANGE
Ans: Soil Colloid
Three types of clays
Ans: Iron and aluminum oxide
non-crystalline silicate clays
crystalline and silicate clays
found in humid tropical climates, highly weathered, ultisols and oxisols
-some may have crystalline structure while others are amorphous
Ans: Iron and Aluminum Oxides
tightly bonded silicon, aluminum and oxygen NO ORDERED
ARRANGEMENT
-volcanic ash, Andisols
Ans: Non-crystalline Silicate Clays
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DOMINANT IN MOST SOILS
-specific crystal structure
Ans: Crystalline Silicate Clay
2 basic structural units of structured clays
Ans: Si Tetrahedron
Al Octahedron
what makes a Sheet
Ans: a series of structural units that are bonded together
what makes a Layer and two types
Ans: Adjacent sheets that are bonded together
-1:1 (Si:Al), tetra:octa SiAl/SiAl
-2:1 (Si:Al), tetra:octa SiAlSi/SiAlSi
what makes a clay particle
Ans: a series of layers
Where does permanent charge of clays come from? 1:1 or 2:1?
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Ans: isomorphous substitution: the replacement of one atom
by another of similar size in the crystal structure
2:1 clays
What is variable charge? 1:1 or 2:1?
Ans: pH dependent charge
all except 2:1...1:1 clays, non crystall, silicate in Fe, Al oxides
-organic mater
-edges of clay (Si-OH)
What is the central atom in Tetrahedron and what is it replaced by?
does it become more negative or positive?
Ans: Si4+
replaced by Al3+
becomes more negative
What is the central atom in Octahedron and what is it replaced by?
more negative or pos?
Ans: Al3+
replaced by Mg2+
becomes more negative
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1:1 silicates
Ans: Kaolinite is most common
-halloysite, nacrite, and dickite
2:1 silicates
Ans: Illite, Chlorite, Vermiculite, Montorillonite
3 types if 2:1 silicates
Ans: 2:1 non expanding
2:1:1 chlorite
2:1 expanding
Kaolinite
Ans: 1:1
non-expanding
interlayer hydrogen bond (superglue)
large
NO ISOMORPH SUB, NO PERM CHARGE, surface charge is low
OCT-TET/H+/OCT-TET
All rights reserved © 2025/ 2026 |
SOIL 2124 EXAM 3 Questions and Correct
Answers/ Latest Update / Already Graded
mineral or organic particles in soil having a diameter less than 1um
(0.000001 m)- CLAY SIZE RANGE
Ans: Soil Colloid
Three types of clays
Ans: Iron and aluminum oxide
non-crystalline silicate clays
crystalline and silicate clays
found in humid tropical climates, highly weathered, ultisols and oxisols
-some may have crystalline structure while others are amorphous
Ans: Iron and Aluminum Oxides
tightly bonded silicon, aluminum and oxygen NO ORDERED
ARRANGEMENT
-volcanic ash, Andisols
Ans: Non-crystalline Silicate Clays
All rights reserved © 2025/ 2026 |
, Page |2
DOMINANT IN MOST SOILS
-specific crystal structure
Ans: Crystalline Silicate Clay
2 basic structural units of structured clays
Ans: Si Tetrahedron
Al Octahedron
what makes a Sheet
Ans: a series of structural units that are bonded together
what makes a Layer and two types
Ans: Adjacent sheets that are bonded together
-1:1 (Si:Al), tetra:octa SiAl/SiAl
-2:1 (Si:Al), tetra:octa SiAlSi/SiAlSi
what makes a clay particle
Ans: a series of layers
Where does permanent charge of clays come from? 1:1 or 2:1?
All rights reserved © 2025/ 2026 |
, Page |3
Ans: isomorphous substitution: the replacement of one atom
by another of similar size in the crystal structure
2:1 clays
What is variable charge? 1:1 or 2:1?
Ans: pH dependent charge
all except 2:1...1:1 clays, non crystall, silicate in Fe, Al oxides
-organic mater
-edges of clay (Si-OH)
What is the central atom in Tetrahedron and what is it replaced by?
does it become more negative or positive?
Ans: Si4+
replaced by Al3+
becomes more negative
What is the central atom in Octahedron and what is it replaced by?
more negative or pos?
Ans: Al3+
replaced by Mg2+
becomes more negative
All rights reserved © 2025/ 2026 |
, Page |4
1:1 silicates
Ans: Kaolinite is most common
-halloysite, nacrite, and dickite
2:1 silicates
Ans: Illite, Chlorite, Vermiculite, Montorillonite
3 types if 2:1 silicates
Ans: 2:1 non expanding
2:1:1 chlorite
2:1 expanding
Kaolinite
Ans: 1:1
non-expanding
interlayer hydrogen bond (superglue)
large
NO ISOMORPH SUB, NO PERM CHARGE, surface charge is low
OCT-TET/H+/OCT-TET
All rights reserved © 2025/ 2026 |
