课程名称︰土壤化学
课程性质︰农化系大三必修
课程教师︰王尚礼
开课学院：生农学院
开课系所︰农化系
考试日期（年月日）︰2015.1.7.交
考试时限（分钟）：一周
本学期无期末考，但要写作业二作业三
试题 :
1. The data in the table presented here refer to Cu(II) adsorption by an
Aridisol.
(1) Plot an adsorption isotherm with the data and classify the isotherm.
(2) Cauulate and plot Kd as a function of N for the data.
Cu
(3) Fit the data using Freudlinch equation and calculate the isotherm
parameters.
(4) Fit the data using linear form of Langmuir isotherm and calculate the
isotherm parameters.
┌──────┬───┬────┬────┬────┬────┬────┐
│N (mmol/kg)│ 6.78 │ 10.64 │ 18.05 │ 25.39 │ 34.14 │ 37.34 │
│ Cu │ │ │ │ │ │ │
├──────┼───┼────┼────┼────┼────┼────┤
│C (mmol/kg)│ 1.87 │ 3.06 │ 9.19 │ 28.11 │ 77.78 │ 155.1 │
│ Cu │ │ │ │ │ │ │
└──────┴───┴────┴────┴────┴────┴────┘
2. Experimental measurements indicate that a soil suspended in CaHPO solution
4
+ _ 0 _
contains tne surface species SOH , SOH, SO , (SO )Ca , and SHOP , where
2 2 4
0
SOH refers to 1 mol of reactive surface hydroxyl groups; (SO )Ca and
2
_
SHPO are inner-sphere complexes. Give expressions for σH , σIS ,
4
σOS , and σD in terms of the concentrations of the surface species.
0
(e.g., [SOCa ])
3. When the anti biotic ciprofloxacin is in the presence of MnO , the
2+ 2
antibiotics disappears from solution and Mn begins to appear in the
solution. The rate of antibiotic loss decreases as pH increases, but
increases with the initial concentration of both the antibiotic and the
Mn oxide. Discuss the hypothesis that the loss of the antibiotic results
from a surface-controlled reductive dissolution reaction. What additional
experiments would be useful for testing the hypothesis?
4. Calvulate a conditional exchange equilibuium constant for the reaction
2+ 2+
MgX + Ca = CaX +Mg based on the data in the table presented here.
2 2
Mg/Ca
Plot Kv against E . Does the adsorbent exhibit preference?
Ca
──────────────────────────────────────
C
Mg(molc/kg) 20.4 17.8 14.8 12.4 10.1 4.9 2.4 1.2
──────────────────────────────────────
C (molc/kg) 2.4 4.8 7.2 9.7 12.3 17.0 19.6 20.9
Ca
──────────────────────────────────────
q (molc/kg) 0.21 0.17 0.14 0.12 0.093 0.053 0.027 0.016
Mg
──────────────────────────────────────
q (molc/kg) 0.078 0.11 0.15 0.17 0.21 0.26 0.31 0.30
Ca
──────────────────────────────────────
5. Calculate the difusion coefficient of a soil colloid with a radius of 1 μm
o
that moves through water at 25 C . According to an analysis by
Albert Einstein, the time required for a colloid to diffuse a distance △x
3
is 2(△x) / 3D. Estimate the time required for the soil colloid to diffuse
10 μm and compare the result with the time required by an ion (please find
reference data on internet)
6. Explain the chemical basis for the statement: Organic matter prevents the
dispersion of dry soil aggragates; once the soil particles in the
aggragates are forced apart (by shaking in suspension) , however, the
organic matter heops to stabilize the separated particles in suspension."
7. It is observed experimentally that the concentration of synthetic organic
polymer cation required to coagulate suspensions of clay minerals is
proportional to the initial solids concentration. Use this result to
suggest a mechanism for the colagulation process.