1. Which one of the following is most likely to be an ionic compound?

a.   CaCl₂

b.   CO₂

c.   CS₂

d.   SO₂

2. Which one of the following is most likely to be an ionic compound?

a.   ClF₃

b.   FeCl₃

c.   NH₃

d.   PF₃

3. Which one of the following is most likely to be a covalent compound?

a.   Rb₂O

b.   BaO

c.   SrO

d.   SeO₂

4. Which one of the following is most likely to be a covalent compound?

a.   KF

b.   CaCl₂

c.   SF₄

d.   Al₂O₃

5. The Lewis dot symbol for the lead atom is:

6. The Lewis dot symbol for the S ^2- ion is:

7. Which one of the following ionic solids would have the largest lattice energy?

a.   NaCl

b.   NaF

c.   CaBr₂

d.   CaCl₂

8. Which of the following ionic solids would have the largest lattice energy?

a.   SrO

b.   NaF

c.   CaBr₂

d.   CsI

9. Which of the following solids would have the highest melting point?

a.   NaF

b.   NaCl

c.   NaBr

d.   NaI

10. Which of the following solids would have the lowest melting point?

a.   KI

b.   KBr

c.   KCl

d.   KF

11. Which of the elements listed below has the greatest electronegativity?

a.   Na

b.   As

c.   Ga

d.   Cs

12. Which of the elements listed below is the least electronegative?

a.   Sr

b.   V

c.   Ni

d.   P

13. Which of the bonds below would have the greatest polarity (i.e., highest percent ionic character)?

a.   Si ¾ P

b.   Si ¾ S

c.   Si ¾ Se

d.   Si ¾ Cl

14. The Lewis structure for CS₂ is:

15. Assuming the octet rule is obeyed, how many covalent bonds will a nitrogen atom form to give a formal charge of zero?

a.   0

b.   1

c.   2

d.   3

16. Which of the following is a useful guideline for the application of formal charges in neutral molecules?

a.   A Lewis structure in which there are no formal charges is preferred.

b.   Lewis structures with large formal charges (e.g., +2,+3 and/or -2,-3) are preferred.

c.   The preferred Lewis structure is one in which positive formal charges are on the most electronegative atoms.

17. For which of these species does the best Lewis structure have two or more equivalent resonance structures?

a.   HCO₂^-

b.   SCN^-

c.   CNO^-

d.   N₃^-

18. Which one of the following compounds does not follow the octet rule?

a.   NF₃

b.   CF₄

c.   PF₅

d.   AsH₃

19. Which one of the following compounds does not follow the octet rule?

a.   NF₃

b.   CO₂

c.   CF₄

d.   NO

20. Use the bond enthalpy data given to estimate the heat released when 6.50g of nitrogen gas reacts with excess hydrogen gas to form ammonia at 25°C.  BE(N?N) = 941.4 kJ/mol, BE(H-H) = 436.4 kJ/mol, BE(N-H) = 393 kJ/mol

a.   228 kJ

b.   340 kJ

c.   107 kJ

d.   24.9 kJ

21. Give the number of lone pairs around the central atom and the molecular geometry of CBr₄.

a.   0 lone pairs, square planar

b.   0 lone pairs, tetrahedral

c.   1 lone pair, square pyramidal

d.   1 lone pair, trigonal bipyramidal

22. Give the number of lone pairs around the central atom and the molecular geometry of SCl₂.

a.   0 lone pairs, linear

b.   1 lone pair, bent

c.   2 lone pairs, bent

d.   3 lone pairs, bent

23. According to the VSEPR theory, the geometry of the SO₃ molecule is:

a.   pyramidal.

b.   tetrahedral.

c.   trigonal planar.

d.   distorted tetrahedron (seesaw).

24. According to the VSEPR theory, the molecular geometry of ammonia is:

a.   linear.

b.   trigonal planar.

c.   bent.

d.   trigonal pyramidal.

25. The bond angle in SCl₂ is expected to be:

a.   a little less than 109.5°.

b.   109.5°.

c.   a little more than 109.5°.

d.   120°.

26. The bond angle in Cl₂O is expected to be approximately:

a.   90°.

b.   109.5°.

c.   120°.

d.   145°.

27. Complete the following sentence: The PCl₅ molecule has:

a.   nonpolar bonds, and is a nonpolar molecule.

b.   nonpolar bonds, but is a polar molecule.

c.   polar bonds, and is a polar molecule.

d.   polar bonds, but is a nonpolar molecule.

28. Which one of the following molecules has a non-zero dipole moment?

a.   BeCl₂

b.   Br₂

c.   BF₃

d.   IBr

29. Which one of the following molecules has a zero dipole moment?

a.   CO

b.   CH₂Cl₂

c.   SO₃

d.   SO₂

30. Indicate the type of hybrid orbitals used by the central atom in CCl₄.

a.   sp

b.   sp²

c.   sp³

d.   sp³d

31. Indicate the type of hybrid orbitals used by the central atom in SF₆.

a.   sp

b.   sp²

c.   sp³

d.   sp³d²

32. What is the hybridization on the central atom in NO₃^- ?

a.   sp

b.   sp²

c.   sp³

d.   sp³d

33. Which of the following is not true of molecular orbitals?

a.   The number of molecular orbitals formed is always equal to the number of atomic orbitals combined.

b.   A molecular orbital can accommodate up to two electrons.

c.   When electrons are added to orbitals of the same energy, the most stable arrangement is predicted by Hund's rule.

d.   For any substance, the number of electrons in molecular orbitals is equal to the sum of all the valence electrons on the bonding atoms.

34. Which of the following correctly lists species in order of increasing bond length?

a.   O₂ < O₂⁺ < O₂^-

b.   O₂^- < O₂ < O₂⁺

c.   O₂⁺ < O₂ < O₂^-

d.   O₂^- < O₂⁺ < O₂

35. The N - N - H bond angles in hydrazine N₂H₄ are 112°.  What is the hybridization of the nitrogen orbitals predicted by valence bond theory?

a.   sp³

b.   sp²

c.   sp⁴

d.   sp⁶