SWS3022 Lectures Questions with Correct Answers
Which of the following has an influence over the preference of cations at charged clay surfaces? - Answer-size
charge
concentration in solution
A chemical element that has acquired an electrical charge by losing an electron during a reaction is...
SWS3022 Lectures Questions with
Correct Answers
Which of the following has an influence over the preference of cations at charged clay
surfaces? - Answer-size
charge
concentration in solution
A chemical element that has acquired an electrical charge by losing an electron during a
reaction is called a/an - Answer-ion
Which of the following would be most preferred at charged silicate clay surfaces all else
being equal? - Answer-AI3+
Organic carbon in soils - Answer--can act similarly to organic solvents like hexane or
octanol
-can increase the half-life of organic compounds by shielding them from degradation
-can sequester or store synthetic organic chemicals like DDT for long periods of time
Water insoluble organic chemicals are usually polar or charged - Answer-False
Factors Determining Cation Preference - Answer-1. Concentration in solution
2. Charge (+1, +2,+3)
3. Cation Size
All three simultaneously contribute to affinity for charged sites
Hydration sphere size varies widely depending on the ion - Answer-true
Smaller cations are preferred at negative sites - Answer-true
Charge and Size: Charge Density - Answer-charhe density: charge/size
Indication of how tightly cations are held at exchange sites
(at equivalent concentrations)
Capacity to Adsorb Cations - Answer-("Adsorption" occurs at surfaces)
Mineral Cation Exchange Capacity - Answer-The total quantity of cations a
clay can adsorb.
Related directly to the amount of
isomorphous substitution
Equal to the amount of charge
Units are cmolc/kg soil
, Range: 0 - 180 cmolc/kg
What is a Centimole? - Answer-1/100 of a mole
1mole = 6.02 x 1023 charges
1cmol = 6.02 x 1021 charges
1 cmol = 6,020,000,000,000,000,000,000 charges
Range: 0 - 180 cmolc/kg
Charge density is a clay's charge in relation to its size - Answer-false
A 1:1 mineral has - Answer-one tetrahedral sheet and 1 octahedral sheet
A 2:1 mineral has - Answer-one octahedral sheet and 2 tetrahedral sheets
Small cations are attracted to colloid surfaces more strongly than large cations. -
Answer-true
Cation A has a +3 charge and is small. Cation B has a +1 charge and is large. Which is
more likely to occupy negatively charged sites on a clay mineral given equal
concentrations in solution? - Answer-cation a
Cations are positively charged. - Answer-true
Anions are negatively charged. - Answer-true
Charge is developed on silicate clay minerals during mineral formation. - Answer-true
The charge on soil clays is satisfied by anions from soil solution. - Answer-false
Highly charged cations are attracted to soil colloid surfaces more strongly that weakly
charged cations. - Answer-true
Isomorphous substitution typically results in a net negative charge on soil clay minerals.
- Answer-true
organic chemical - Answer-also referred to as an organic compound, is defined as being
constructed of molecules that possess carbon-based atoms. Specifically, it is composed
of carbon atoms attached to hydrogen atoms, together with a variety of other elements
from functional groups, such as oxygen, nitrogen, sulfur, etc. Usually, an organic
chemical is covalently bonded, meaning that electrons are shared between atoms. This
characteristic is why organic chemicals can be structured in a variety of long chains and
rings and form bonds with the great stability. Can be naturally-occurring or synthetic in
nature.
Inorganic solution constituents may contain
carbon, but are not based generally
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