4. Which of the following statements regarding EDTA titration are correct?
(1) Back-titration should be used if analyte does not have satisfactory indicator.
(2) If the pH is lowered, the conditional formation constant decreases, and the end point becomes more distinct.
 (3) The pH cannot be raised arbitrarily high, because metal hydroxide might precipitate.
 (4) Anions that precipitate with certain metal ions can be analyzed with EDTA by displacement titration method.
(5) Trivalent cations can usually be titrated without interference from divalent species by maintaining the solution even at a pH = 1.
 Your answer:
(A) (1) and (5)；
(B) (1), (3) and (5)；
(C) (1), (3) and (4)；
(D) (2), (4) and (5)；
(E) (1), (2) and (3).

100. 鋼索的直徑減少達公稱直徑多少百分比以上者，不准使用 (A)5％ (B)7％ (C)10％ (D)12％ 。

1. For gravimetric analysis and argentometric titration, which of the following statements are correct? (1) At the equivalence point, the pAgt is dependent of the original concentrations or volumes. (2) At the equivalence point, the pAgt can be found by the solubility product of the precipitate. (3) The larger the equilibrium constant for a titration reaction, the more pronounced will be the change in concentration near the equivalence point. (4) The equivalence point is always at the center of the steepest section of the titration curve no matter of the stoichiometry of reactants. (5) The change in pAg+ at the equivalence point becomes greater as the solubility products become smaller. Your answer: (A) (2), (4) and (5)； (B) (2) and (3)； (C) (2), (3) and (5)； (D) (2) and (5)； (E) The statements are all correct.

2. For ionic strength and activity coefficients, which of the following statements are correct? (1) For 1:1 electrolytes, ionic strength equals the molarity. (2) The larger the ion size, the less important activity effects become. (3) Activity coefficients decrease with increasing ionic strength. (4) Activity coefficients are assumed to be zero for neutral molecules. (5) The greater the ionic strength of the solution, the lower the charge in each ionic atmosphere. Your answer: (A) (1), (2) and (3)；(B) (1) and (3)；(C)(1), (3) and (5)； (D)(3) and (4)； (E) The statements are all correct.

3. Kjeldahl nitrogen analysis is one of the most widely used methods for the determination of nitrogen in organic substances. Which reaction is not involving in this analysis: (A) Kjeldahl digestion by H2SO4 and boiling (B) Neutralization of (C) NH3 gas reaction with excess standard HCl(D) Distillation of NH3 into standard NaOH NH3 + HO- → NH4OH (E) Titration of unreacted HCl H+ OH-→H2O

複選題5. For solvent extraction, which of the following statements are correct? (1) For neutral analytes, many small extractions are less effective than few large extractions. (2) The larger the partition coefficient ([S]2/[S]1) of a neutral analyte, the less the analyte remain in phase 2. (3) To extract the base analytes into organic phase, use a pH high enough to convert BH into  B.(4) To extract the acid HA into organic phase, use a pH low enough to convert A- into HA. (5) Most complexes that can be extracted into organic solvent are neutral, and charged complexes are less soluble in organic solvents. Your answer: (A) (1), (3) and (4)； (B) (2) and (3)； (C)(3), (4) and (5)； (D)(3) and (4)； (E) The statements are all correct.

6. For solid-phase microextraction (SPME), which of the following parameters could not be concerned? (A) type of SPME fiber； (B) pH of sample； (C) extraction time； (D) volume of sample； (E) extraction temperature.

7. For the van Deemter equation and band broadening terms, which of the following statements are correct? (1) Multiple path present in an open tubular column. (2) Longitudinal diffusion increases with diffusion coefficient of solute. (3) Extra column band broadening depends on length and radius of connecting tubing. (4) Equilibration time in stationary phase increases with thickness of stationary phase fim. (5) Equilibration time in mobile phase depends on radius of open tubular column. Your answer: (A) (2), (3), (4) and (5)； (B) (2), (4) and (5)； (C) (3), (4) and (5)； (D) (2) and (5)； (E) The statements are all correct.

8. Chromatograms of compounds A and B were obtained at the same flow rate with two columns of equal length, which of the following statement is not correct? (A) Column 1 has more theoretical plate. (B) Column 2 has a smaller plate height. (C) Column 1 gives higher resolution. (D) Compound B has a higher retention factor. (E) Relative retention is equal for the two columns.

9. Which of the following GC detector is especially sensitive to compounds containing nitrogen and phosphorus. (A) Electron capture detector； (B) Flame ionization detector； (C) Flame photometric detector； (D) Photoionization detector； (E) Alkali flame detector.

10. Which of the following statements about the elution process of LC is not true? (A) In nornal-phase LC, the least polar analyte is eluted first because it is the most soluble in the mobile phase. (B) In normal-phase LC, a less polar solvent has higher eluent strength. (C) Increasing the polarity of the mobile phase has the effect of decreasing the elution time in normal-phase LC.(D) In reversed-phase LC, a more polar solvent has lower eluent strength. (E) In reversed-phase LC, increasing the mobile phase polarity increases the elution time of the less polar analyte.