Jan.10, 2005 Analytical Chemistry
1.Explain the following terms:(12%)
a) iodometry b) Jones reductor
c) chelate effect d) desferroxamine B
2.Consider the titration of 50.0mL of 1.00x10^-3M Zn2+ with 1.00x10^-3M
EDTA at pH 10.0 NH3/NH4Cl buffer which contains 0.10M NH3. Find the pZn2+
after addition of 50.0mL of EDTA. (Note:α for Y4- at pH10.0 is 0.36; logKf
for Zn-EDTA complex is 16.50; For the zinc-ammine complex, β1=10^2.18;
β2=10^4.43; β3=10^6.74; β4=10^8.70) (7%)
3.Please deduce an equation to show the equivalence point potential for the
titration of ferrous ion(Fe2+) in acidic solution with potassium permagnate
(KMnO4) standard solution. (4%)
4.(a) How does the glucose monitor work?
(b) Why is a mediator advantageous in the glucose monitor? (10%)
5.Differential pulse polarography produces a curve (ΔI vs.E) that is nearly
derivative of an ordinary direct current polarogram(I vs. E). The enhanced
sensitivity of pulse polarography relative to that of direct current
polarography is due mainly to an increase in faradaic current and a decrease
in condenser current.
Explain the terms underlined. (20%)
6.What is a Clard electrode and how does it work? Give the cathode and anode
reaction. (8%)
7.Give an example to explain what is done in anodic stripping voltammetry. (6%)
8.Write the chemical reactions to show that 1 mol of I2 is required for 1 mol
of H2O in a Karl Fischer titration. (8%)
9.Explain the reason why a three-electrode cell was used for the
controlled-potential electrolysis. (6%)
10.a) Give three ways that solute gets to electrode. b) Which one is desired
in polarography? c) Which one is not desired in polarography? In this case,
how to improve the condition. (6%)
11.Describe how to determine the chloride concentration with potentiometric
titration. (8%)
12.Suppose we wish to determine the silver ion concentration in an unknown
sample solution by means of direct potentiometry. Please illustrate how to
do it. (8%)
13.The voltammograms of a)1mM O2 in acetonitrile with 0.10M (C2H5)4N+ClO4-
electrolyte and b)0.060mM 2-nitropropane in acetonitrile with 0.10M
(n-C7H15)4N+ClO4- electrolyte are shown in the following. Please describe
the voltammograms and explain the meaning of the marks labeled. Besides,
please indicate the difference between these two voltammograms? (15%)
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