Synthesis Lab

Shira Hirsh
Adam Robinson
Mickey Jou
11-10-99
Period 2

Purpouse:
1. To synthesize a compound and compare its properties with those of the elements from which it is formed.
2. To determine the composition of the compiund in terms of the masses and mass percentages of the elements of which it is composed.
3. To understand the Law of Definite Proportions
4. To observe changes which occur during a chemical reaction
5. To learn to express a reaction in terms of a simple equation
6. To gain insight into the meaning of chemical formulas
In short, burn some stuff, don't blind yourself, and make some observations on it.

Procedure:
1. Get the necessary materials: Magnesium ribbon; crucible and cover; clay triangle; ring stand; burner; balance; tongs; metal scoop.
2. List the properties of the reactants.
3. Get a ball of magnesium ribbon.
4. Heat said magnesium in the crucible until it catches on fire. Then place the cover on the crucible, removing periodically to let oxygen flow in and out.
5. Once all the magnesium ribbon is burned, adjust the cover so that a steady stream of air can flow in and out.
6. Pulverize the contents of the crucible. Add 5-10 drops of water.
Heat gently for 3-4 minutes, note odor, then heat strongly for 3-4 minutes. 7. Weigh the crucible and the contents.
8. Fill in the chart.
9. Clean everything up.
Data/Observations:

1.	Mass of Crucible, cover, and magnesium	21.85 grams	Balance
2.	Mass of crucible and cover	21.54 grams	Balance
3.	Mass of magnesium used	0.33 grams	21.85-21.54
4.	Mass of crucible, cover and product	21.97 grams	Balance
5.	Mass of crucible plus cover	21.54 grams	Balance
6.	Mass of compound formed	0.43 grams	21.97-21.54
7.	Mass of magnesium used	0.33 grams	Balance
8.	Mass of oxygen in compound	0.10 grams	0.43-0.33
9.	Percentage of oxygen in compound	23.26%	0.10/0.43
10.	Percentage of magnesium in compound	76.74%	0.33/0.43
11.	Percentage deviation from theoretically calculated value	27.9%	((76.74-60.00)/60.00)*100

Substance	Element or compound	Metal or nonmetal	Physical Phase	Color	Combustibility	Symbol or formula
Magnesium	Element	Metal	Solid	Gray/Silver	Yes	Mg
Oxygen	Element	Nonmetal	Gas	Colorless	No	O 2
Magnesium Oxide	Compound	Neither	Solid	Gray/White	No	MgO

Analysis and Conclusions:
The MgO lab assigned by the instructor was a rather interesting one. Simply put, we were given some magnesium to heat up in the crucible, watered the ashes down, then heated it again to perform a decomposition exercise. How successful the lab turned out to be, however, is another story. The data collected did not correspond to the theoretical value of the percent composition numbers derived by the instructor. The data number is, in fact, 17% higher than the theoretical value. Some of the possible explanation for the "extra mass" may be that the lab was not performed correctly. That is to say, that perhaps the magnesium nitride were not completely separated and disposed of during the experiment, as the ashes did not seemed to be completely submerged in the water. Another possibility may be that some of the remains of past chemical experiment on the crucible tongs might have got mixed up with the MgO.




Home