Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 110

Chem 110, Dr. Paselk

Hour Exam 2

 Name
Fall 2002

(100 pts)
 Lab

If you want to look at/print out a copy of the EXAM + ANSWERS click here. You may then return to the exam by clicking on your browser's BACK key.

This examination is scheduled for fifty (50) minutes. At the end of this fifty minute period you will have five (5) minutes to bring your examination to the front of the examination room.

 

1. (10 @ 2 ea) True/False. Indicate whether the following statements are True (T) or False (F).

Diamagnetism is due to paired electrons in an atom or molecule. _______________

An atom with dsp3 hybridization will have a trigonal bipyramidal electronic geometry. _______________

Hybrid orbital theory is based on a localized electron model. _______________

The Group VA elements are an excellent example of the trend of increasing metallicity with increasing atomic size in a group. _______________

The inert pair effect may explain the behavior of Group VIIIA elements. _______________

 

2. (21 @ 3 ea) Answer the following in the spaces provided.

How many allotropes exist for carbon under normal conditions? _______________

Give the formula of the strongest of the chlorine oxyacids _______________

Would you expect the oxide of Sn or Sb to be the stronger base? _______________

What is the formula for white phosphorus? _______________

Would you expect a Te oxide to be acidic, basic, or amphoteric? _______________

List two properties typical of metals generally. _______________

Give an oxidation state for Sb explained by the inert pair effect. _______________

 

3. (8) Sketch a molecular orbital diagram for lithium fluoride showing how the MO's arise from the orbitals of the bonded atoms, including all bonding electrons from each atom before and after bond formation.

 

 

4. (10) a. Draw a Molecular Orbital Energy-level diagram for molecular oxygen, including all valence electrons from each atom.

 

b. What is the bond order for oxygen? Indicate your reasoning or show a calculation based on your diagram for credit.

 

c. Based on your diagram, is this molecule diamagnetic or paramagnetic? Explain (short sentence or phrase).

 

5. (12) Fill in the table below to describe the hybridization and bonding seen for the central atom in each structure.

Molecule

Hybridization

Sigma bonds

Pi bonds

SF4
     

HCN
     

PCl5
     

H2CO
     

 

6. (12) In one of our demonstrations the instructor heated a yellow powder in a test tube over a Bunsen burner. As the contents were heated a yellowish, watery liquid appeared at the bottom of the tube as the powder melted. With continued heating the liquid gradually turned orange and them reddish as the liquid became very viscous. When poured into cold water the viscous liquid turned to a light yellow elastic solid.

a. Explain the change at the molecular level which gives rise to the viscosity change.

 

b. What will happen to the elastic material obtained at the end? Why?

 

c. During the demonstration an acrid odor was noted as the experiment proceeded. What is the odiferous gas likely to be? Write an equation for its formation.

 

7. (7) Why do the elements of the second period tend to differ so markedly from the other elements of their groups?

 

 

8. (20) Write the NET ionic equation for the reaction which occurs when the following are mixed. (If there is no reaction, indicate by "NR." )

a. Tin(IV) sulfide is treated with a large excess of sodium hydroxide.

 

b. Bismuth(III) chloride is mixed with hydrogen sulfide in a moderately acidic solution.

 

c. Aluminum metal is added to a solution of tin(IV) in 6M hydrochloric acid (SnCl62-).

 

d. Sulfuric acid is added to a solution of barium chloride.

 

e. Sulfur trioxide is added to water.

 


Syllabus/Schedule
C110 Home

C110 Lecture Notes

© R A Paselk

Last modified 30 October 2006