Partners: Sonya Pasia and Kristen Kobayashi
20 September 2011
Zinc Iodide (ZnI2) was an interesting binary compound to experiment with. In this experiment, weakly acidified water (25mL distilled water with 18 drops 5M acetic acid solution) was used as an aid to bring molecules of the zinc and iodide atoms together, by dissolving iodine molecules, so that bonding would transpire to produce a reaction. Deprived of water, the Zn and I2 molecules would not be capable of moving close enough to each other, and a reaction would not occur. Deprived of acid, the reaction of Zn + I2 would have resulted in 2HI(aq) rather than ZnI2 (s), and it wouldn’t have appeared to follow the Law of Conservation of Mass. The experiment was performed in order to determine if this law is truly followed.
During the experiment, all weight measurements were performed on a balance pan. To ensure accurate measurements, each test tube was weighed before and after addition of any substance with results being recorded as data. Equal amounts of Zn and I2 were weighed out and added to a test tube with 2 boiling stones, Zn being added first. 5 mL of weakly acidified water was added to the tube and swirled. The properties of reaction were recorded. After determining if the solution was I2 or Zn(I3) 2 (aq), the solution was stirred until all color dissipated, and poured into a 22 x 175 mm test tube without pouring the Zn metal out. The zinc metal was washed with 1mL of acidified water 3 times, with water being discarded into the tube, and 3 times with water being discarded in the sink. The Zn metal was dried over a Bunsen burner ensuring all liquid was removed, and weighed to obtain the amount of Zn that had been consumed. The ZnI2 was passed over the Bunsen burner, ensuring that all liquid was evaporated, and the test tube was weighed.
The measurements were added together to determine if the Law of Conservation of Mass had been