Chemistry 122S
Summer 1998
Oregon State University
Exam 1
July 23, 1998
Dr. Richard Nafshun

Name __________________________________________ Score ___________ / 100

[Periodic Table Provided Here]

Identify Ionic and Covalent Bonds--5 Points

1. Which of the following is an ionic compound?

(a) O₃.

(b) O₂.

(c) CaCl₂.

(d) CH₃COOH.

(e) CH₃CH₂OH. 

Give Lewis Symbols for Atoms, Molecules, Ions, and Polyatomic Ions--5 Points Each

2. Give the Lewis Symbol for PH₃ (please include all electrons).

3. Give the Lewis Symbol for formic acid, HCOOH (please include all electrons).

 Calculate the Overall Energy Change for a Given Reaction--10 Points

4. For lithium, the enthalpy of sublimation is +161 kJ/mol and the first ionization energy is +520 kJ/mol. The dissociation energy of chlorine is +122 kJ/mol Cl₂, and the electron affinity of chlorine is -349 kJ/mol. The lattice energy of LiCl is -852 kJ/mol. Calculate the overall enthalpy change for the reaction

Li (s) + 1/2 Cl₂ (g) ---> LiCl (s) D H°_f = ?

Discuss Metals and Non-Metals and their Reactivity Behavior--5 Points

5. Which of the following elements is commonly stored in oil because it readily reacts with air?

(a) Xenon.

(b) Oxygen.

(c) Nitrogen.

(d) Carbon.

(e) Sodium.

Discuss Equal and Unequal Sharing of Electron Pairs in Covalent Bonds--5 Points

6. Draw the Lewis Symbol for CF₄ and indicate the relative position of the bonding electrons.

 

Discuss Bond Lengths, Energies, and Orders--5 Points

7. Which of the following molecules contains the shortest carbon-carbon bond length?

(a) C₂H₂.

(b) C₂H₄.

(c) C₂H₆.

 

 

 

Using Formal Charges, Predict Stable Lewis Structures--10 Points

8. Draw ONE Lewis Symbol for sulfur dioxide, SO₂; determine the formal charges for each element in the molecule and comment on the stability of the structure.

 

 

Discuss Saturated and Unsaturated Hydrocarbons--5 Points

9. Draw an unsaturated hydrocarbon which contains at least six carbons. You need not include electrons, but just the skeletal structure.)

 

Discuss Polymers--5 Points

10. Which of the following molecules can undergo polymerization in the presence of an initiator?

(a) C₂H₃F.

(b) C₂H₆.

(c) C₂H₅F.

(d) C₃H₈.

(e) C₃H₇F.

 

Predict Molecular Shapes (Molecular Geometries and Bond Angles)--5 Points

11. The H-N-H bond angle in NH₃ is

(a) 90° .

(b) A little less than 109.5° .

(c) Exactly 109.5° .

(d) A little more than 109.5° .

(e) Exactly 120° .

Discuss Polar and Non-Polar Molecules--5 Points Each

12. An example of a non-polar molecule is __________________.

13. An example of a polar molecule is ______________________.

Create and Interpret MO Energy Diagrams--10 Points

14. Consider F₂ (g). Create an MO energy diagram, fill-in the electrons, and determine the bond order for fluorine-fluorine bond.

Identify the Hybridization of Carbon in Organic Compounds--5 Points

15. Label the hybridization for each carbon in the following organic compound:

Construct and Interpret Resonance Structures--10 Points

16. Carbon is the central atom in the carbonate ion, CO₃^2-. Draw the three resonance structures for the carbonate ion and indicate the bond order for the carbon to oxygen bond.