14. Which one of the following descriptions about GC (gas chromatography) is correct?
(A) In GC, the stationary phase is liquid or solid, the mobile phase is gas.
(B) It can only be applied for gaseous samples.
(C) In order to obtain a complete separation, different gaseous mixtures are purged into the column successively.
(D) GC is not an efficient separation technique.
(E) All of these are correct.

10. Which statement about N2 is false? (A) It is a gas at room temperature. (B) The oxidation state is +3 on one N and -3 on the other. (C) It has one sigma and two pi bonds between the two atoms. (D) It can combine with H2 to form NH3. (E) It has two pairs of nonbonding electrons.

11. Which of these statements about benzene is true? (A) All carbon atoms in benzene are sp3 hybridized. (B) Benzene contains only π bonds between C atoms. (C) The bond order of each C—C bond in benzene is 1.5. (D) Benzene is an example of a molecule that displays ionic bonding. (E) All of these statements are false.

12. When electrons in a molecule are not found between a pair of atoms but move throughout the molecule, this is called . (A) ionic bonding (B) covalent bonding (C) polar covalent bonding (D) delocalization of the electrons (E) a dipole moment

13. Which one of the following descriptions for microelectrodes is incorrect? (A) The dimensions of such electrodes are usually smaller than about 20 μm. (B) The IR (current × resistance) drop of microelectrodes is higher than traditional electrodes. (C) Such electrodes can be used for the study of chemical processes in single cells. (D) They are also called ultramicroelectrodes or microscopic electrodes. (E) By using such electrodes, three electrodes system is not necessary.

15. Which one of the following detectors is not used for HPLC (high-performance liquid chromatography)? (A) Absorbance detectors (B) Fluorescence detectors (C) Electrochemical detectors (D) Flame ionization detectors (E) Mass spectrometers

16. Which one of the following descriptions about CE (capillary electrophoresis) is incorrect? (A) Electrophoresis is a separation technique based on the different migration rates of charged species. (B) It cannot be used to separate proteins and nucleic acids. (C) Its particular strength is the unique ability to separate charged macromolecules. (D) Until the appearance of CE, electrophoretic separations were not carried out in columns. (E) Most of the detectors used for HPLC can be employed for CE.

17. The pH meter is widely used for measuring the H+ concentrations in the solutions. Which one of the following descriptions for a pH is incorrect? (A) The sensing material is a special thin glass membrane at the tip of the electrode. (B) No reference electrode is required for a pH meter. (C) The real signal obtained from the pH meter is voltage (or difference of potentials). (D) In basic solutions, the indicator electrode also responds to alkali metal ions. (E) pH meters can be used to determine the equivalence point of the acid-base titration.

18. Atomic spectrometer is widely applied for the analysis of various elements. Which one of the following is not an atomization method used for most atomic spectrometer? (A) Flame (B) Inductively coupled plasma (C) Electrothermal oven (D) Laser (E) Electric spark

19. A method of separation that employs a system with two phases of matter, a mobile phase and a stationary phase, is called               . (A) filtration (B) chromatography (C) distillation (D) vaporization (E) homogenization

20. A solution is also called a               . (A) homogeneous mixture (B) heterogeneous mixture (C) pure mixture (D) compound (E) distilled mixture