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）︰deadline 2014.12.31
考试时限（分钟）：一周
本作业视同期末考之一部份，本学期没有期末考。
试题 :
1. (1) Develop a balanced redox reaction for fulfate reduction to bisulfide
coupled to glucose oxidation to bicarbonate. (2) Use the appropriate
reactions in the lecture note to prepare a pE - pH diagram for S based
2- _
on the aqueous species SO , H S and HS .
4 2
2. Bacteria of the genus Nitrobacter catalyze the oxidation of nitrite to
nitrate using O as an electron acceptor. Write a balanced overall redox
2
reaction for this proces and calculate log K. What will be the
_ _
concentration ratio of NO to NO when pE = 7 at pH 6
3 2
3+ 2+
3. (1) Find the pH at which (Fe ) = (Fe ) at Po = 0.21 atm
2
2+ -5
(2) If measured pH = 7.0 and (Fe ) = 1.0 X 10 M, what is pe?
4. The PZC of a variable-charge soil is 5.0. After a phosphate fertilizer is
applied to the soil, it is observed that the soil retains more adsorbed
cations at pH 5 than before. Explain in terms of surface charge balance
why this effect occurs.
-1
5. The data here show the pH dependence of qk and q (in mmol kg ) for
NO3
-1
an Oxisol suspended in 10 mmol L KNO . Plot △q = qk - q as a function
3 NO3
of pH and determine the PZC ( or PZNC) for the soil.
——————————————————————————————————————
qk q pH qk q pH
NO3 NO3
——————————————————————————————————————
0.7 6.6 2.5 4.0 3.5 3.9
1.3 5.1 2.8 4.2 3.0 4.1
2.5 4.7 3.2 4.9 1.5 4.6
2.3 4.3 3.6 6.3 1.2 4.9
2.6 4.0 3.7 9.5 0.6 5.3
——————————————————————————————————————