19. How many unpaired electr rons does cobalt have in its ground state?
(A) 7
(B) 27
(C) 5
(D)3
(E)1

15. For the reaction . Therefore, the reaction under standard conditions is (A) spontaneou us only at temperatures between 10 K and 800 K (B) spontaneous at temperatures greater than 800 K (C) spontaneous at all temperatures (D) nonspontaneous at all temperatures (E) spontaneous at temperatures less than 10 K

16. When a battery dies, which of the following is true? (A)△G° = 0 (B)△G = O (C) E°= O (D) Q= 1 (E) A and C

17. Which of the following statements is/are true of the electrolysis of brine? I: chlorine is produced at the anode of the cell during the electrolysis of brine；Il: under normal circumstances, sodium is produced at the cathode of the cell during the electrolysis of brine； III: hydrogen is produced at the cathode of the cell during the electrolysis of brine. (A) I only (B) II only (C) III only (D) I and II (E) I and Ill

18. How many f orbitals have the value n = 3? (A) 3(B) 1 (C)0(D) 5(E)7

20. Which of the following exhibits the correct orders (increasing) for atomic radius and ionization energy, respectively? (A) F, S, O, and O, S, F (B) F, O, s, and s, O, F (C) s, O, F, and F, O, s (D) S, F, O, and S, F, O (E) none of these

21. 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? BH3, NO2, SF6, O3 and PCl5 (A) 2 (B) 4 (C) 1 (D) 3 (E) they are all polar.

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

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