27.In the unit cell of sphalerite, ions occupy half the tetrahedral holes in a face-centered cubic lattice ions. What is the number of formula units of ZnS in the unit cell?
(A) 3
(B) 5
(C) 4
(D) 1
(E) 2

23. How many of the following molecules have all of their atoms in the same plane? H2C = CH2, F2O, H2CO,NH3, CO2, BeC2 and H2O2 (A) 4 (B) 5 (C) 6 (D) 7 (E) 3

24. Which of the following statements about the ion is false? (A) the ion has a total of 24 electrons (B) the orbitals on the carbon atom are sp2 hybridized (C) the ion is expected to be diamagnetic (D) one C-O bond is shorter than the others (E) it has a planar molecular geometry

25. An ethyl group that is attached to a substituent that does not contain a hydrogen atom appears as what in a NMR spectrum? (A) a triplet and a quartet with relative intensities of 3 and 2, respectively (B) a triplet and a quartet with relative intensities of 2 and 3, respectively (C) a doublet and a triplet with relative intensities of 2 and 3, respectively (D) a doublet and a triplet with relative intensities of 3 and 2, respectively (E) none of these

26. How many of the following has a bond order = 0.5? (A) 2(B) 3 (C)4 (D) 1 (E)0

28. Which of the compounds below is an example of a network solid? (A) NaCl(s) (B) S8(s) (C) MgO(s) (D) SiO2(S) (E)

29. A certain substance, X, has a triple-point temperature of 20℃ at a pressure of 2.0 atm. Which one of the following statements cannot possibly be true? (A) X can exist as a liquid above 20℃  (B) both liquid and solid X have the same vapor pressure at 20℃ (C) liquid X can exist as a stable phase at 25℃ , 1 atm (D) X can exist as a solid above 20℃  (E) all of these statements could be true

30. The density of the solid phase of a substance is 0.90 g/cm3 and the density of the liquid phase is 1.0 g/cm3 . A large increase in pressure will (A) lower the freezing point (B) lower the boiling point (C) lower the triple point (D) raise the triple point (E) raise the freezing point.

31. Which of the following is the most polarizable? (A) Ar (B) He (C) Kr (D) Ne (E) Xe

32. For which of the following compound(s) are cis and trans isomers possible? (A) difluoroethyne (B) 2,3-dichloro-2-butene (C) 3,4-diethyl-3-hexene (D) ortho-chloroanaline (E) 4,4-dimethylcyclohexanol

33. Aspirin is formed via a(r)_______ reaction. (A) combustion (B) hydrogenation (C) condensation (D) substitution (E) addition