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FIRE AND BRIMSTONE (REACTIONS OF SULFUR)

* PURPOSE

The purpose of this activity is to illustrate some of the reactions of sulfur.

* DESCRIPTION

This activity is appropriate for a general or first-year college-prep course. Reactions of sulfur with zinc, iron and oxygen will be performed. The concept of competing reactions will also be introduced. The term "brimstone" is used in the title since it is a common name for sulfur and one that students may know.

* TIME REQUIRED

One lab period.

* MATERIALS

Chemicals:
flowers of sulfur*
0.10 M H2SO4 (dilute 5.6 mL concentrated sulfuric acid solution to 1.0 L with distilled or deionized water)
galvanized nails--#8
common iron nails or 0000 steel wool*
Equipment:
nichrome wire
centigram balance
Bunsen burner
glass plate (or microscope slide)
file
magnet
*See Modifications / Substitutions

* HAZARDS

Caution should be used to avoid burns from the hot nichrome wire or from the hot reaction mixtures. Sulfur dioxide is an irritating, toxic gas; hydrogen sulfide is extremely poisonous. Although the quantities of sulfur dioxide and hydrogen sulfide produced in this experiment are small, the reactions should be carried out in a hood or well-ventilated room. Students should be cautioned not to inhale the smoke produced. The teacher can limit the amount of products formed by passing out the sulfur personally at the beginning of the experiment. If good ventilation is not available, the teacher may want to do this as a demonstration to limit quantities even further. Goggles must be worn throughout the experiment.

* MODIFICATIONS/SUBSTITUTIONS

  1. Flowers of sulfur is available from a drugstore or nursery.
  2. Sulfuric acid is available from an auto supply store as battery acid.
  3. Galvanized and iron nails are available at hardware stores.

* PROCEDURE

  1. Place an amount of sulfur equal to about 1/2 the size of a pea on the glass plate.
  2. Mass 1/4 of a sheet of notebook paper, and record this mass. Obtain 4 galvanized nails and file the zinc coating from the nails onto this paper. Pass a magnet over these filings to remove any iron, and then mass the paper with the filings.
  3. Calculate the amount of sulfur needed for the correct stoichiometric ratio of zinc to sulfur based on the mass of zinc obtained.
  4. Mass this amount of sulfur and add it to the zinc. Mix to a homogeneous color. Pour a pile of onto the glass plate next to the pile of sulfur. Make these two piles equal in size.
  5. File an iron nail to obtain some iron filings or cut steel wool into fine pieces and mass on a pre-massed piece of paper.
  6. Calculate the amount of sulfur needed for the correct stoichiometric ratio of iron to sulfur for this reaction
  7. Mass this amount of sulfur and add it to the iron. Mix to a homogeneous color. Then pour a pile equal to the amount of the original sulfur pile on the glass plate next to the other two piles.
  8. Put a loop in one end of a nichrome wire. Place the wire loop into the flame of a Bunsen burner. Touch the red hot wire to the sulfur pile. Record results. Repeat the procedure for the other two piles. If the mixtures do not ignite, place the residue that sticks to the nichrome wire into the burner.
  9. (Optional) In a hood, place 1 drop of 0.10 M H2SO4 on the iron sulfide. Carefully waft the odor of the product of this reaction toward your nose and note the characteristic odor of hydrogen sulfide. This is the gas that comes from some geysers and is a constituent of swamp gas.

* DISPOSAL

The products of this lab are insoluble and should not go down the drain. Dispose of them with solid waste.

* DISCUSSION

Burning sulfur in air will produce sulfur dioxide.
S (s) + O2 (g) ----> SO2 (g)
In the second reaction,competing reactions will produce not only zinc sulfide, but also zinc oxide and sulfur dioxide.
Zn (s) + S (s) ----> ZnS (s)

2 Zn (s) + O2 (g) ----> 2 ZnO (s)
Zn sulfide will appear as a yellow-white solid. Zinc oxide can be seen as a white smoke (colloidal solid), and sulfur dioxide is a colorless gas. In the third reaction, iron sulfide and sulfur dioxide are formed.
Fe (s) + S (s) ----> FeS (s)
Iron sulfide is a black, insoluble solid which will react with mineral acids to produce hydrogen sulfide (H2S).

* REFERENCES

Brown, T.L. and Lemay, H.E., Jr., Chemistry: The Central Science, Prentice Hall, Englewood Cliffs, NJ, 1981, p. 655. This work describes some of the reactions of sulfur.

Shakhashiri, B.Z., Chemical Demonstrations: Volume One, University of Wisconsin Press, Madison, 1983, p. 53. Large scale reactions of sulfur with iron and zinc are described.

Submitted by Doug Rickard and Sam Sakurada


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