CHM 1045 Exam 4 CH 9 amp 10 Sp13 1

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CHM 1045: Exam 4 – Chapters 9 & 10

Chapter 9: Chemical Bonding I – Lewis Theory

1. Which of the following statements is TRUE?

a) A covalent bond is formed through the transfer of electrons from one atom to another.
b) A pair of electrons involved in a covalent bond are sometimes referred to as "lone pairs."
c) It is not possible for two atoms to share more than two electrons.
e) A covalent bond has a lower potential energy than the two separate atoms.
d) Single bonds are shorter than double bonds.

2. Which of the following represent the Lewis structure for Cl?

a)
c)
d)
b)
e)

3. Which of the following represent the Lewis structure for Br-?

a)
b)
c)
d)
e)

4. Identify the substance that conducts electricity.

c) water (H2O)
d) solid sugar (C6H12O6)
e) sugar (C6H12O6) dissolved in water.
a) Table salt (NaCl) dissolved in water
b) solid table salt (NaCl)

5. Use Lewis theory to determine the chemical formula for the compound formed between Rb and S.

a) RbS
b) RbS2
d) Rb2S3
c) Rb2S
e) Rb3S2

6. Choose the compound below that should have the highest melting point according to the ionic bonding model.

b) MgO
c) NaF
d) CaS
a) AlN
e) RbI

7. Use the data given below to construct a Born-Haber cycle to determine the lattice energy of KCl. H°(kJ) Sublimation of potassium K(s) → K(g) 89 Ionization energy of potassium K(g) → K+ (g) + e- 418 Bond energy of chlorine Cl2(g) → 2 Cl(g) 244 Electron affinity of chlorine Cl(g) + e- → Cl- (g) -349 Lattice energy of potassium chloride K+ (g) + Cl-(g) → KCl(s) ? Heat of formation of potassium chloride K(s) + ½ Cl2(g) → KCl(s) -437

a) -1537 kJ
b) -663 kJ
e) -717 kJ
c) -157 kJ
d) -839 kJ

8. Choose the bond below that is most polar.

c) H-F
d) H-Cl
b) H-Br
a) H-I
e) C-H

9. Which molecule or compound below contains a polar covalent bond?

a) C2H4
d) NCl3
b) ZnS
c) LiI
e) AgCl

10. The phosphorus atom in PCl3 would be expected to have a

b) partial negative (δ-) charge.
a) partial positive (δ+) charge.
c) 3+ charge.
d) 3- charge.

11. Choose the best Lewis structure for OCl2

a)
b)
e)
c)
d)

12. Choose the best Lewis structure for XeI2

c)

a)

b)

d)

e)

13. Choose the best Lewis structure for NO3-
c)

a) b) d) e)

Chapter 10: Valence Bond Theory and Molecular Orbital Theory

Consider the molecule below to answer questions 14-16.

14. Determine the molecular geometry at each of the 3 labeled atoms in the molecule above

a) 1=trigonal planar, 2=tetrahedral, 3=trigonal pyramidal
b) 1=tetrahedral, 2=tetrahedral, 3=tetrahedral
c) 1=trigonal planar, 2=tetrahedral, 3=tetrahedral
d) 1=tetrahedral, 2=tetrahedral, 3=trigonal planar
e) 1=trigonal planar, 2=trigonal pyramidal, 3=trigonal pyramidal

15. Determine the hybridization at each of the 3 labeled atoms in the molecule above?

a) 1=sp2, 2=sp3, 3=sp2
b) 1=sp2, 2=sp3, 3=sp3
c) 1=sp3, 2=sp3, 3=sp3
d) 1=sp3, 2=sp3, 3=sp2
e) 1=sp, 2=sp2, 3=sp2

16. What is the total number of sigma bonds () and pi bonds () in the molecule above?

a) 7 and 2 b) 8 and 1 c) 2 and 7 d) 1 and 8 e) 9 and 0

17. Determine the electron geometry (eg) and molecular geometry(mg) of BCl3

a) eg=trigonal planar, mg=trigonal planar
b) eg=tetrahedral, mg=trigonal planar
c) eg=tetrahedral, mg=trigonal pyramidal
d) eg=trigonal planar, mg=bent
e) eg=trigonal bipyramidal, mg= trigonal bipyramidal

18. Determine the electron geometry (eg) and molecular geometry (mg) of PF5

a) eg=trigonal bipyramidal, mg=trigonal bipyramidal
b) eg=octahedral, mg=octahedral
c) eg=trigonal bipyramidal, mg=tetrahedral
d) eg=tetrahedral, mg=trigonal pyramidal
e) eg=trigonal planar, mg=octahedral

19. Determine the electron geometry (eg) and molecular geometry (mg) of CO32-

a) eg=tetrahedral, mg=tetrahedral
b) eg=tetrahedral, mg=trigonal pyramidal
c) eg=trigonal planar, mg=bent
d) eg=trigonal planar, mg=trigonal planar
e) eg=tetrahedral, mg=trigonal planar

20. Determine the electron geometry (eg) and molecular geometry (mg) of the underlined atom in: CH3OCH3

a) eg=tetrahedral, mg=tetrahedral
b) eg=linear, eg=linear
c) eg=tetrahedral, mg=bent
d) eg=trigonal bipyramidal, mg=tetrahedral
e) eg=octahedral, mg=square planar

21. Identify the number of electron groups around a molecule with sp hybridization.

a) 1
b) 2
c) 3
d) 4
e) 5

22. A molecule containing a central atom with sp2 hybridization has a(n) __________ electron geometry.

a) linear
b) trigonal bipyramidal
c) trigonal planar
d) tetrahedral
e) bent

23. Choose the compound below that contains at least one polar covalent bond, but is nonpolar.

a) HCN
b) CF4
c) SeBr4
d) ICl3
e) Both B and C are nonpolar and contain a polar covalent bond.

24. Which of the following statements is TRUE?

a) The total number of molecular orbitals formed doesn't always equal the number of atomic orbitals in the set.
b) A bond order of 0 represents a stable chemical bond.
c) When two atomic orbitals come together to form two molecular orbitals, one molecular orbital will be lower in energy than the two separate atomic orbitals and one molecular orbital will be higher in energy than the separate atomic orbitals.
d) Electrons placed in antibonding orbitals stabilize the ion/molecule.
e) All of the above are true.

Refer to the molecular orbital diagram below to answer questions 25-27:

25. Use the molecular orbital diagram shown to determine which of the following are paramagnetic.

a) F2
b) F22+
c) Ne22+
d) O22+
e) F22-

26. Use the molecular orbital diagram shown to determine which of the following is most stable.

a) F2
b) F22+
c) Ne22+
d) O22+
e) F22-
27. What is the bond order for the molecule F22- ?

a) 0 b) 0.5 c) 1.0 d) 1.5 e) 2.0