55. What two atomic orbitals or hybrid atomic orbitals overlap to form the C-C π bond in ethylene?
(A)CSp³ + CSp³
(B)Csp³ + Csp²
(C)Csp² + Csp²
(D)Csp² + Cp
(E)CP + CP

51. Which of the following is the most reactive carboxylic acid derivative? (A) ester (B) anhydride (C) nitrile (D) acid chloride (E) amide

52. Lithium aluminum hydride reduces carboxylic acids, acid chlorides, and esters to. (A) aldehydes. (B) primary alcohols. (C) secondary alcohols. (D) tertiary alcohols. (E) ketones.

53. Cyclic amides are called: (A) lactones. (B) lactams. (C) aminals. (D) animals. (E) mines.

54. The structures below are: (A) not isomers. (B) conformational isomers. (C) cis-trans isomers. (D) structural isomers. (E) both B and D

56. The following three equations represent equilibria that lie far to the right. Identify the ongest base. (A) CH3O- (B) CH3OH (C) CN- (D) H2O (E) N03-

57. If the molarity a 0.70 M solution ofhypochlorous acid，HCIO was decreased to 0.3 M, which of the following statements would be true? (A) The percent dissociation would not change. (B) The percent dissociation would increase. (C) The percent dissociation would decrease. (D) The equilibrium constant would stay the same. (E) Two of these.

58. If 30 mL of 5.0 x 10-4M Ca(NO 3)2 are added to 70 mL of 2.0 ✖ 10-4 M NaF, will a precipitate occur? (Ksp of CaF2 = 4.0 ✖ 10-11 ) (A) No, because the ion product is greater than iTSp. (B) Yes, because the ion product is less than XSp. (C) No, because the ion product is less than ZSp. (D) Not enough information is given. (E) Yes, because the ion product is greater than Ksp.

59. A galvanic cell consists of a left compartment with a tin electrode in contact with 0.1 M Sn(N03)2(aq) and a right compartment with a lead electrode in contact with 1 ✖ 10 -3M Pb(NO3)2(aq). The relevant reduction potentials are:   When this cell is allowed to discharge spontaneously at 25°C, which of the following statements is true? (A) Electrons will flow from left to right through the wire. (B) Pb2+ ions will be reduced to Pb metal.  (C) the concentration of Sn2+ ions in the left compartment will increase. (D) The tin electrode will be the cathode. (E) No noticeable change will occur, because the cell is at equilibrium.

60. Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment): The standard reduction potentials are as follows: Which of the following statements about this cell is false? (A) This is a galvanic cell. (B) Electrons flow from the Pt electrode to the Cr electrode. (C) Reduction occurs at the Pt electrode. (D) The cell is not at standard conditions. (E) To complete the circuit, cations migrate into the left half-cell and anions migrate into the right half-cell from the salt bridge. II. Choose one correct answer for the following questions

61. Which of the following compounds is the strongest acid? (A)p-nitrobenzoic acid (B)p-bromobenzoic acid (C) m-methylbenzoic acid (D) m-methoxybenzoic acid (E) water