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SWS3022 Exam 3 Chapter 9-12 | Questions And Answers Latest {} A+ Graded | 100% Verified $13.48   Add to cart

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SWS3022 Exam 3 Chapter 9-12 | Questions And Answers Latest {} A+ Graded | 100% Verified

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SWS3022 Exam 3 Chapter 9-12 | Questions And Answers Latest {} A+ Graded | 100% Verified

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SWS3022 Exam 3 Chapter 9-12 | Questions And Answers Latest {2024- 2025} A+ Graded |
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What is mineral formation? - When aluminosilicates dervive charge from substitution of lower-charged
cations for higher charged cations in the crystal matrix



What charge results from mineral formation? - permanent negative charge



What substitution happens during mineral formation? - - Al3+ for Si4+

- Mg2+ for Al3+



What do charges on silicate crystal edges and on Al/Fe oxides depend on? - protonation and
deprotonation (results in variable, pH-dependent charge



What do organic colloids derive their charge from? - protonation/deprotonation of hydrogen ions from
acidic functional groups on humic organic materials



What is an acid? - any substance which increases the hydrogen ion concentration in solution

pH of 0-7

high H+ concentration



What are sources of acids? - - atmosphere: respiration from microorganisms

- acid functional groups on organic matter

ammonium oxidation: nitrification and fertilizers



T/F charge balance must be maintained when plants uptake cations - true



Which side of the US has acidic vs basic rain? - - eastern US has acidic rain

- western US has basic rain

,What is a base? - any substance that decreases the hydrogen ion concentration in solution

OH- and CO3 ^2-

pH of 4-14

low H+ concentration



What are the two ions considered acidic in soils? - H+ and Al

- both are cationic

- Al participates in hydrolysis reactions with water



What is the hydrolysis of water? - - self-ionization of water

- H2O -> OH- + H+

H+ is the acid

OH- is the base

- in pure water, H+ and OH- amounts are equal



What is hydrolysis by aluminum? - - Al splits water and reacts with resulting OH-

H2O -> OH- + H+

Al3+ + H2O = Al(OH)2+ + H+

Al(OH)2+ + H2O = Al(OH)2+ + H+



What is active acidity? - - acidity associated with soil solution

- this is what is measured when you take the pH of the soil (measure with a pH meter)

- cations held in solution



How do you measure active acidity? - - 1:1 or 2:1 extract (10g soil and 10 mL water or 10g soil and 20 mL
water)



What is the pH formula concerning log? - pH = -log(H+)

-pH = log(H+)

, 10^-pH = 10^log(H+)

10^-pH = (H+)mol/L



What is exchangeable acidity? - - H+, Al3+Al(OH)2+, and Al(OH)2+ are all cations

- acidity associated with cation exchange sites on mineral or organic colloids

- aka salt-replaceable acidity

- 100-1,000x more than in active acidity

- allows it to contribute to the pH of soil

- cations held near minerals and materials



What is residual acidity? - tightly bound to clay minerals and humic organic materials



What is the formula for total acidity? - total acidity = active + exchangeable + residual



T/F Acids increase the H+ concentrations in solution - true



Acidity associated with the soil solution is called: - active acidity



Identify one source of H+ ions to soil - atmosphere (respiration from microorganisms)



T/F Rainfall is naturally acidic - true



The two ions considered acids in soils are: - H+ and Al



Is CEC a good indication of fertility? - no

- CEC suggests ability of soil to store plant nutrients



Describe an example of ion saturation with a CEC of 20 cmolc/kg - Ca = 10 cmolc/kg (50%)

Mg = 3 cmolc/kg (15%)

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