27. Draw the Lewis structures of the molecules below, and use them to answer the following questions. How many of the molecules have no dipole moment?

 I: BH₃, II: NO₂, III: SF₆, IV: O₃, V: PC1₅
(A) 1
(B) 2
(C) 3
(D) 4
(E) they are all polar

23. When a nonvolatile solute is added to a volatile solvent, the solution vapor pressure , the boiling point _, the freezing point _, and the osmotic pressure across a semipermeable membrane . (A) decreases, increases, decreases, decreases (B) increases, increases, decreases, increases (C) increases, decreases, increases, decreases (D) decreases, decreases, increases, decreases (E) decreases, increases, decreases, increases

24. The destruction of a colloid is called (A) degeneration (B) coagulation (C) denaturation (D) reconfiguration (E) none of these

25. How many of the following molecules have all of their atoms in the same plane? H2C=CH2, F2O, H2CO, NH3, CO2, BeCl2, H2O2 (A) 3 (B) 4 (C) 5 (D) 6 (E) 7

26. What is the shape of the ICl5 molecule? (A) square pyramid (B) trigonal bipyramid (C) octahedral (D) see-saw (E) none of these

28. Which of the following statements about the species N2, CO, is false? (A) all are isoelectronic (B) each contains a triple bond (C) all are linear. (D) the bond in each species is polar (E) all incorrect

29. The Cl-Kr-Cl bond angle in KrCl4 is closest to (A) 90° (B) 109° (C) 120° (D) 150° (E) 360°

30. In the molecular-orbital description of CO, (A) the highest energy electrons occupy antibonding orbitals (B) six molecular orbitals contain electrons (C) there are two unpaired electrons (D) the bond order is 3 (E) all of these are false

31. Which of the following is diamagnetic? (A) (B) (C) B2 (D) F2 (E) ВО

32. Which of the following statements is true? (A) electrons are never found in an antibonding MO (B) all antibonding MOs are higher in energy than the atomic orbitals of which they are composed (C) antibonding MOs have electron density mainly outside the space between the two nuclei (D) none of these statements is true (E) two of these statements are true

33. Based on intermolecular forces, which of the following will have the highest boiling point? (A) PF5 (B) SF4 (C) AsF5 (D) more information is needed to answer the question (E) all are liquids