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

21. Solid KF has a lattice energy of -804 kJ/mol and a heat of solution (in water) of -15 kJ/mol. RbF has a lattice energy of -768 kJ/mol and a heat of solution (in water) of -24 kJ/mol. Which salt forms stronger attractions with water? (A) KF, because it has a more exothermic lattice energy (B) RbF, because it has a less exothermic lattice energy (C) KF, because it has a more negative heat of hydration (D) RbF, because it has a more negative heat of hydration (E) they form equally strong attractions with water, because they both have negative heats of mixing

22. Liquid A has vapor pressure x. Liquid B has vapor pressure y, and x ＞ y. What is the mole fraction of A in the liquid mixture if the vapor above the solution is 30% A? (A) 0.3y/(0.7x + 0.3y) (B) 0.7y/(0.3x + 0.7y) (C) 0.3x/(0.3x + 0.7y) (D) 0.7x/(0.7x + 0.3y) (E) none of these

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

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

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

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