課程名稱︰分析化學乙下
課程性質︰
課程教師︰林萬寅
開課系所︰
考試時間︰2004.4.13
試題 :
1. The cell SCE|HA(0.005M), NaA(0.08M)|H2(1.00atm)|Pt
develops a potential of -0.80V (HA is an unknown weak acid) 10%
(a) Write the balanced cell reaction.
(b) Calculate Ka for HA. (E* for SCE=0.241V)
2. A solution of Sn(2+) (40ml, 0.010M) was titrated with 0.020M Ce(4+)
in 1M H2SO4. [Ef(Ce4+ --> Ce3+)= 1.44V ; Ef(Sn4+ --> Sn2+)= 0.77V]
(a) Calculate the equilibrium constant for the titration reaction.
(b) Calculate the electrode potential after addition of 20.0ml Ce(4+).
(c) Calculate the electrode potential after addition of 40.0ml Ce(4+).
(d) Calculate the electrode potential after addition of 50.0ml Ce(4+).
3. A 50.0ml sample of orange juice gave a peak current of 2.00uA in an
amperometric analysis. A standard addition of 1.00ml of 25.0mM ascorbic
acid increased the peak current to 3.00uA. Find the concentration of
ascorbic acid in the orange juice. 10%
4. Apotransferrin has a molar absorptivity of 8.8x10^4 M^-1 cm^-1 at 280nm.
(a) Find the concentration of apotransferrin if the absorbance is 0.44
in a 0.10-cm cell.
(b) Calculate the percentage of light that was absorbed by the solution
in (a).
5. What is electrogravimetry? How can you know when an electrogravimetric
deposition is complete?
6. What is the difference between faradaic and charging current? How does
sampled current polarography reduce the contribution of the charging
current to the polarogram?
7. Explain the following terms.
(a) Junction potential
(b) Ion-selective electrode
(c) Three-electrode system
(d) Striping analysis
(e) Coulometry
(f) Selectivity coefficient
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