Semester 1 Review Problem Set b

This problem set was developed by S.E. Van Bramer for Chemistry 145 at Widener University.

Acetylene (C2H2) is a gas that is commonly used for welding. The reaction used is the combustion of Acetylene and O2. Based upon this system you should be able to answer the following questions that show your understanding of the first semester of chemistry.

  1. Write a balanced equation for the reaction.

  2. Draw lewis dot structures of all reactants and products.

  3. Describe the geometry and hybridization of the reactants and products.

  4. Draw an energy level diagram that shows the molecular orbitals of the homonuclear diatomic molecules.

  5. Determine Hrxn for the balanced equation.

    Acetylene is sold as a gas that has been dissolved in acetone (Under pressure the pure gas is explosive). It is priced by weight. If you purchase a cylinder with 20.0 pounds of acetylene.

    1. How many moles of acetylene?
    2. How many molecules of acetylene?
    3. Assuming acetylene is an ideal gas, how many liters and m3 of acetylene is this at STP?

  6. For welding, O2 is supplied by a compressed gas cylinder. You also purchase a cylinder of O2 that has a volume of 4 cuf and a pressure of 3000 psi. Assuming that the O2 behaves as an ideal gas:

    1. How many grams of O2
    2. How many moles of O2

  7. If you completely use the two cylinders, what volume of products is produced? (The temperature of an oxy-acetylene torch is approximately 5700 F)

  8. How much heat is produced by the complete reaction of the two cylinders?

  9. How much hot water would this produce for a hot water heater? Assume a starting temperature of 10 C, and a final temperature of 180 F.

Please send comments or suggestions to

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

© copyright 1996, S.E. Van Bramer
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Last Updated: Saturday, May 18, 1996