Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chemistry 107

Chem 107

Hour Exam II
Fall 1996

(100 pts)
  Lab Section (circle): Tu Th

If you want to look at/print out a copy of the EXAM + ANSWERS click here. This will give you a copy of the Key without spaces saving much paper and and thus forest products! You may then return to the exam by clicking on your browser's BACK key. Note that questions 5, 6, 9 & 10 do not apply to this years exam, but they will apply to the final.


(12) 1. Write Lewis Dot Structures for each of the following:

 a. Si



b. CaO

 c. H2CO



d. HCN

(12) 2. Consider H2CO & HCN (c & d above). What is:
 The steric number for: c. d.
 The electronic geometry for: c. d.
 The molecular geometry for: c. d.

(4) 3. Would you expect H2CO (c above) to be polar? Explain.

(12) 4. Consider the reaction of hydrochloric acid and iron metal to give ferrous chloride (iron II chloride) in solution (as ions) and hydrogen gas as products.

a. Write a balanced, net ionic, equation for this reaction.

b. What is the oxidizing agent in your equation?

c. Which species is oxidized?

d. What is the reductant?

(15) 5. Consider the chemical reaction diagram below:


a. Label the axis on this diagram

b. Show on the diagram: reactants and products; activation energy (Ea), and the change in free energy (DG).

c. Is this reaction exergonic or endergonic?

d. Is this reaction spontaneous? Explain briefly.


(10) 6. Two moles of NOCl gas are placed in a 5.00-liter container at 25°C. NOCl is known to decompose slightly to NO and Cl2gases. If the equilibrium constant for this reaction is 2.0 x 10-10 what are the concentrations of all species at 25°C? SHOW all work! NO CREDIT for lone answers!

(10) 7. Consider the cylinder of an engine in an automobile. Assume that the cylinder is filled with a gas at 756.0 mmHg of pressure at 30.0°C, and that it has a volume of 450.0 ml when the piston is all of the way down. The piston then compresses the gas to 40.0 ml and ignites the mixture, raising the temperature to 827°C. Assuming there are the same total number of moles of gas before and after reaction, calculate the new pressure, in atm, in the cylinder. SHOW all work! NO CREDIT for lone answers!

(10) 8. Assume that you "empty" an aerosol spray can of paint in your garage. on the back of the can you note that it has a volume of 475 mL. If the temperature is 23°C and atmospheric pressure is measured to be 764 mmHg, how many moles of gas remain in the can? SHOW all work! NO CREDIT for lone answers!

(10) 9. Consider the reaction below:

2 NO(g)+ O2(g) Æ 2 NO2(g)+  H

a. Write the Mass Action Expression for this reaction.

b. What will happen to this reaction if the volume is increased?

c. What will happen to the [O2] if the temperature is decreased?

(5) 10. Why do reaction rates increase with increasing temperature?



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