課程名稱︰分析化學丁
課程性質︰必修
課程教師︰林萬寅
開課系所︰生命科學系
考試時間︰2006.6.26 10:20~12:10
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試題 :
1.Answer the following questions.
(a) Explain how solid-phase microextraction work.
(b) How many lines/cm should be etched in the grating if the second order
diffration for 600 nm is to be -20度 when the incident angle is 30度?
(c) Explain how cold trapping work?
(d) Describe the principle of thermal conductivity detector for GC detection?
(e) What is the purpose of a matrix modified in atomic spectroscopy?
(f) Explain how to prepare deionized water using ion-exchange resins?
(g) Suggest plausible formulas for CnHxOyNz if M+=123 and (M+1)+/M+ = 6.1%.
(h) How does a CO2-sensing compound electrode work?
(i) Describe the principle of the hollow cathode lamp.
(j) Describe the Faradaic and charging current.
2.Selenium from 0.12g of nuts was converted into the fluorescent product
which was extracted into 50.0mL of hexane. Then 2.0mL of the hexane solution was
placed in a cuvet for fluorescence measurements and gave an intensity of
40.0. Standard addtion of 50.0μL fluorescenct product containing 1.50μg
Se/mL to the cuvet gave a fluorescence intensity of 75.0. Find the
percentage of Se in the nuts.
3.Consider a negatively charged protein tightly adsorbed on an anion exchange
gel at pH 8.0. Explain how you would elute the protein out of the column
with (a) a pH gradient and (b) a gradient in ionic strength.
4.A 1.0-L electrolysis cell initially containing 0.030M Mn2+ and another metal
ion, M3+, is fitted with Mn and Pt electrodes. A constant current of 2.50A
was passed through the cell for 20 min causing 0.54g of the metal M to plate
out on the Pt electrode. (F=96485C)
(a) What is the atomic mass of M?
(b) What will be the concentration of Mn2+ in the cell at the end of the
experiment?
5.Consider the titration of 40.0ml of 0.0050M Sn2+ by 0.010M Ce2+ in 1M HCl,
using Pt cathode and saturated calomel electrodes. The formal potentials for
Sn4+→Sn2+ and Ce4+→Ce3+ are 0.14 and 1.47V, respectively. Ef(SCE)=0.241V.
Find the cell potential after the addition of (a) 10mL and (b) 40mL of Ce4+.
6.The retention times(tr) and half-widths(w1/2) for compounds A and B eluted
from a GC column that is 30.0m long are given below.
┌─────┬────┬─────┐
│Compound │tr(min) │W1/2(min) │
├─────┼────┼─────┤
│A │ 14.56│ 0.12│
├─────┼────┼─────┤
│B │ 14.77│ 0.16│
└─────┴────┴─────┘
(a) Find the number of theoretical plates and the plate height for
compound A.
(b) Find the resolution between compounds A and B.
(c) Find the standard deviation(σ) of the elution pea for compound A.
7.A molecular exclusion column has a diameter of 8.0mm and a length of 25cm.
The solid portion of the particles occupied 20% of the volume, the pores
occupy 40%, and the volume between particles occupied 40%.
(a) At what volume would totally excluded molecules be expected to emerge?
(b) At what volume would the smallest molecules be expected?
(c) A molecule is eluted at 14.5mL. What does this imply about the retention
mechanism for this molecule on the column?
8.A solution contains 0.10M IO3-, 0.10M I-, 1mM I3-, and pH 5.0 buffer.
Consider the reaction: 2IO3- + I- + 12H+ + 10e- →I3- + 6H2O; E0=-1.210V
and I3- + 2e- →3I-; E0=0.535V.
(a) Balance the cell reaction and find its equilibrium constant.
(b) Find the cell potential.
(c) At what pH would the given concentrations of IO3-, I- and I3- be in
equilibrium?
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