31. Consider the molecular-orbital description of the anion. Which of the following statements is false?
(A) is paramagnetic
(B) is isoelectronic with CO
(C) the bond energy in is greater than the bond energy in
(D) the bond order in is 2
(E) II of these statements are false

27. Which ion is planar? (A) (B) (C)(D) (E)

28. The bond angles about the carbon atom in the formaldehyde molecule, H2C = O, are about (A) 120°(B) 60°(C) 109°(D) 180°(E) 90°

29. How many of the following molecules and ions are linear? (A) 0(B) 1 (C) 2 (D) 3(E) 4

30. Consider the following molecules, and select the molecule(s) that fit the given statement. I: BF3, H: CHBr3, M: Br2, TV: XeCl2, V: CO, VI: SF4These molecules violate the octet rule. (A) I,lI, IV (B) I, III, IV, VI (C) III, V, VI (D) I, IV, VI (E) I, II, IV, VI

32. For how many of B2, C2, P2, and F2 does bond order decrease if one electron is removed from the neutral molecule? (A) 0(B) 1 (C) 2 (D) 3 (E) 4

33. Order the following from shortest to longest bond: C2, B2, H2, N2 (A) H2, N2, C2, B2 (B) N2, C2, B2, H2 (C) C2, N2, H2, B2 (D) C2, B2, H2, N2 (E) none of these

34. Of the three cubic unit cells, which lattice packing leaves the least amount of free space in the cell? (A) simple cubic (B) body centered cubic (C) face centered cubic (D) need cell dimensions to determine this (E) hexagonal

35. A liquid placed in a closed container will cvaporate until equilibrium is reached. At equilibrium, which of the following statements is not true? (A) the partial pressure exerted by the vapor molecules is called the vapor pressure of the liquid (B) liquid molecules are still evaporating (C) the number of vapor molecules remains essentially constant (D) the boundary (meniscus) between the liquid and the vapor disappears (E) all of these statements are true

複選題36. A p-type semiconductor (A) is made by doping host atoms with atoms having more valence electrons than the host (B) is made by doping host atoms with atoms having fewer valence electrons than the host (C) has electrons that lie close in energy to the conduction bands (D) two of these (E) none of these

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