CSES 2040: Exam 2 UPDATED ACTUAL
Questions and CORRECT Answers
Which of the following substitution creates a net negative charge on a neutral soil?
a. one Ca+2 ion for one K+1 ion
b. one Al+3 ion for one Si+4 ion
c. one Al+3 ion for one Fe+3 ion
d. all of the above - CORRECT ANSWER - b. one Al+3 ion for one Si+4 ion
Soils rich in which type of colloids would provide the most suitable material on which to build
homes and/or roads?
a. humus
b. kaolinite
c. smectite
d. all are about the same - CORRECT ANSWER - b. kaolinite
The two main sources of charges in soil are the permanent (constant) charge and the pH
dependent charge.
a. True
b. False - CORRECT ANSWER - a. True
________ is the amount of cation charges that a soil can hold at its natural or apparent pH.
a. CEC at pH=7.0
b. neutral pH
c. CEC at pH=8.2
d. Effective CEC - CORRECT ANSWER - d. Effective CEC
As the intensity of weathering on clay minerals increases, its cation exchangeable capacity
decreases.
,a. True
b. False - CORRECT ANSWER - a. True
The CEC of an organic soil will:
a. decrease as pH increases
b. increase as pH increases
c. remain the same
d. none of the above - CORRECT ANSWER - b. increase as pH increases
A given soil has significant amount of NH4+ on its exchangeable sites from NH4+ application.
If you use NH4+ to displace the cations and measured the CEC by summation of the displaced
cations, you will _______ CEC of the soil.
a. overestimate
b. underestimate
c. estimate the correct
d. none of the above - CORRECT ANSWER - b. underestimate
An alkaline soil contains 20% clay and 3% humus. If the pure clay has a CEC of 40cmolc/kg and
the humus 200cmolc/kg, calculate the CEC (cmolc/kg) of the soil.
a. 8
b. 30
c. 14
d. 16 - CORRECT ANSWER - c. 14
If pH of a soil is7, its pOH will be:
a. 7
b. 14
c. 6
d. a and b - CORRECT ANSWER - a. 7
, A soil at pH 4.0 will have ______ H+ activity compared to a soil at pH 8.0.
a. 4000x more
b. 4000x less
c. 10,000x more
d. 10,000x less - CORRECT ANSWER - c. 10,000x more
If a growing plant root takes K+1, NH4+1, and SO4-2 from soil solution concurrently, the pH of
the solution will:
a. increase
b. decrease
c. remain the same
d. cannot be determined - CORRECT ANSWER - c. remain the same
Active soil acidity is a measure of the H+ ion activity in the soil solution.
a. True
b. False - CORRECT ANSWER - a. True
If you want to decrease your soil pH very fast, elemental sulfur (S) will be your best choice.
a. True
b. False - CORRECT ANSWER - b. False
Alkalinity, salinity, and sodicity are common problems in arid and semiarid soils.
a. True
b. False - CORRECT ANSWER - a. True
If you dissolve 200g of salt in 1000mL of water and added to your plant, and 700mL of the
solution is lost by evapotranspiration, the amount of salt left in the solution will be:
Questions and CORRECT Answers
Which of the following substitution creates a net negative charge on a neutral soil?
a. one Ca+2 ion for one K+1 ion
b. one Al+3 ion for one Si+4 ion
c. one Al+3 ion for one Fe+3 ion
d. all of the above - CORRECT ANSWER - b. one Al+3 ion for one Si+4 ion
Soils rich in which type of colloids would provide the most suitable material on which to build
homes and/or roads?
a. humus
b. kaolinite
c. smectite
d. all are about the same - CORRECT ANSWER - b. kaolinite
The two main sources of charges in soil are the permanent (constant) charge and the pH
dependent charge.
a. True
b. False - CORRECT ANSWER - a. True
________ is the amount of cation charges that a soil can hold at its natural or apparent pH.
a. CEC at pH=7.0
b. neutral pH
c. CEC at pH=8.2
d. Effective CEC - CORRECT ANSWER - d. Effective CEC
As the intensity of weathering on clay minerals increases, its cation exchangeable capacity
decreases.
,a. True
b. False - CORRECT ANSWER - a. True
The CEC of an organic soil will:
a. decrease as pH increases
b. increase as pH increases
c. remain the same
d. none of the above - CORRECT ANSWER - b. increase as pH increases
A given soil has significant amount of NH4+ on its exchangeable sites from NH4+ application.
If you use NH4+ to displace the cations and measured the CEC by summation of the displaced
cations, you will _______ CEC of the soil.
a. overestimate
b. underestimate
c. estimate the correct
d. none of the above - CORRECT ANSWER - b. underestimate
An alkaline soil contains 20% clay and 3% humus. If the pure clay has a CEC of 40cmolc/kg and
the humus 200cmolc/kg, calculate the CEC (cmolc/kg) of the soil.
a. 8
b. 30
c. 14
d. 16 - CORRECT ANSWER - c. 14
If pH of a soil is7, its pOH will be:
a. 7
b. 14
c. 6
d. a and b - CORRECT ANSWER - a. 7
, A soil at pH 4.0 will have ______ H+ activity compared to a soil at pH 8.0.
a. 4000x more
b. 4000x less
c. 10,000x more
d. 10,000x less - CORRECT ANSWER - c. 10,000x more
If a growing plant root takes K+1, NH4+1, and SO4-2 from soil solution concurrently, the pH of
the solution will:
a. increase
b. decrease
c. remain the same
d. cannot be determined - CORRECT ANSWER - c. remain the same
Active soil acidity is a measure of the H+ ion activity in the soil solution.
a. True
b. False - CORRECT ANSWER - a. True
If you want to decrease your soil pH very fast, elemental sulfur (S) will be your best choice.
a. True
b. False - CORRECT ANSWER - b. False
Alkalinity, salinity, and sodicity are common problems in arid and semiarid soils.
a. True
b. False - CORRECT ANSWER - a. True
If you dissolve 200g of salt in 1000mL of water and added to your plant, and 700mL of the
solution is lost by evapotranspiration, the amount of salt left in the solution will be:
