課程名稱︰分析化學丁
課程性質︰生科系必修
課程教師︰林萬寅
開課系所︰化學系
考試時間︰2006.04.17
試題 :
1. Write the (A) charge balance equation, (B) mass balance equation, and
(C) all pertinent reactions and their equilibrium constant expressions
for the saturated aqueous solution of Ca3(PO4)2.
2. (A) Calculate the activity coefficients for H+ and CH3COO-, knowing that
the hydrated radius is 900 pm for H3O+ and 450 pm for CH3COO- and the ionic
strength is fixed at 0.090. (B) Find the pH of 0.10M CH3COOH aqueous
solution fixed at an ionic strength of 0.090. Ka=1.8x10^-5 for CH3COOH.
3. Find the pH of the following solutions.
(a) 0.010M NaH2PO4
(b) 40.0ml, 0.010M NaH2PO4 + 60.0ml, 0.010M NaOH
(c) 40.0ml, 0.001M NaH2PO4 + 80.0ml, 0.010M NaOH
(pK1=2.15, pK2=7.20, pK3=12.15 for H3PO4)
4. Ca2+ (40.0ml, 0.0100M, buffered at pH9.0; log Kf (CaEDTA)=10.7) was
titrated with 0.0200M EDTA. Answer the following questions:
(a) Calculate the conditional formation constant Kf'. (αY=0.054 at pH=9.0)
(b) Find pCa after addition of 20.0ml EDTA.
(c) Find pCa after addition of 22.0ml EDTA.
5. Two students analyzed the nitrogen content (in wt%) of a protein known to
contain 25.40% N and yielded the following results
Student number of measurements Confidence limit(95%)
=================================================================
A 8 24.50~25.30
B 9 24.88~25.48
=================================================================
(a) Are the results of the two students significantly different from the
theoretical value at 90% confidence level?
(b) Calculate the standard deviations for the results of both students.
(c) Calculate the pooled standard deviation from the results of the two
students.
(d) Do the results of the two students differ from each other at 99%
confidence level? (using the pooled standard deviation)
6. Answer the following questions.
(a) What is peptization? How to prevent peptization during precipitate
washing?
(b) Describe the principles of the color changes near the equivalence
point for the indicators used in the Fajans and Volhard methods.
(c) (i) [(18.2±0.4)-(9.6±0.3)]/(4.56±0.06)=?
(ii) 10^-5.640=?
(iii) log 4567=?
(d) What is homogeneous precipitation? Give an example.
(e) What is relative supersaturation(RS)? How does the magnitude of RS
affect the particle size of a precipitate?
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