Taking the A Train Chem 106 Section 12 1. Introduction: This lab focused on showing the reaction that takes place between zinc and iodine using only deionized water instead of acetic acid (or vinegar) as we did in the previous lab by adding acetic acid to zinc iodide. The purpose of this lab was to see how water created the reaction and another compound or precipitate. Focus Question: Zn(OH)2 was the product when zinc and iodine were reacted without the presence of acetic acid in the water.
Confidence Report: I am confident that our data in the experiment was “good data”. We had the expected positive results occur from the identification experiments. We made sure to measure everything correctly. We correctly identified the precipitate Zn(OH)2 by performing the acid and base test on our precipitate. We received a positive result for each test performed for the presence of the zinc hydroxide compound. It was interesting to note the appearance of the zinc hydroxide from only the mixture of zinc, iodine and deionized water.
To me, it did not look as expected. It was a little more “wet” than other precipitates we have worked with and even had to be separated with the centrifuge. We also found ourselves needing to pipette the excess water moisture from our precipitate because it was difficult to decant without also losing the precipitate. Perhaps the “wetness” could have been attributed to the fact that we did not place this precipitate over the Bunsen burner. Even though our precipitate seemed to contain moisture, it was positively Zn(OH)2.
I am confident that our tests were performed correctly and our results were as described in the lab manual. Our Results: The results showed that Zn(OH)2 was what was produced in the experiment. The acid and base tests for Zn(OH)2 showed positive results because zinc hydroxide is an amphoteric oxide and can act as either an acid or a base in a reaction by either losing or gaining a proton. Tests for Zn(OH)2 Acetic Acid Test3ml of 0. 17M added to precipitate. | + positive resultprecipitate dissolved in the acetic acid| Sodium Hydroxide Test1M| + positive resulta colorless and clear solution was formed|
Post Lab Questions: 1. The chemical equation of the formation of zinc hydroxide after zinc and iodine react: 2Zn+I2+2H2O2Zn(OH)2+I2 2. When zinc hydroxide and acetic acid are reacted, the zinc hydroxide dissolves and a clear liquid is formed which contains zinc acetate and water. Because zinc hydroxide is amphoteric, it can either give or receive a proton. When zinc hydroxide reacts with acetic acid, the reaction yields zinc acetate and water. The reaction is as follows: Zn(OH)2 + 2CH3COOHZn(CH3COO) 2 + 2H2O . What is a side reaction? A side reaction is an unwanted chemical reaction that diminishes the yield of the desired product. 4. Acetic acid was used in the synthesis of zinc iodide because an addition of a weak acid prevents the formation of Zn(OH)2 that occurs when zinc and iodine react with deionized water. The formation of the precipitate inhibits the production of the product ZnI2 and may make it seem as if the basic law of conservation of mass was not obeyed.
Since acetic acid and water are both volatile, they can both be easily removed from the solution by heating which would possibly leave behind more ZnI2 . When the acid is not added, it is interesting to observe the Zn(OH)2 precipitate that is formed. A New Inquiry: What if we had heated this precipitate too like in the last experiment to remove all H2O from it? Would the heating have produced different results or would they remain the same since no acetic acid was present? Works cited: definition for “side reaction” found on Wikipedia, http://en. wikipedia. org/wiki/Chemical_synthesis.