Chem Lab Magnesium Chloride

10/29/08 Magnesium and Hydrochloric Acid Lab What the Experiment Was: In this experiment, we were supposed to mix hydrochloric acid with solid magnesium. This was to be done in the lab, with a group of three. Here is the official problem: Starting with solid magnesium and 1 molar Hydrochloric Acid, conduct a metallic single replacement reaction to make 20mL of .5 molar magnesium chloride. Now for the process… Process: 1. The first thing we did was write out the equation, and figure out how much of each reactant we would need to complete the reaction as stated 2. This is the reaction we found, and balanced 3. 4.

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Mg(s) + 2HCl(aq) --> MgCl2 (aq) + H2 (g) We were able to determine that the equation was REDOX, and that the Magnesium would be reduced. To balance this, the Hydrogen would be oxidized two times, hence the H2. With this balanced equation, we were able to determine that 20mL of .5 molar Magnesium Chloride would be .01 moles. (molar = moles/liters) We used the molar relationship to determine that in order to conduct the reaction, we would need .01 moles of solid magnesium and .02 moles of Hydrochloric acid. This means, we needed .24 grams of Magnesium, and 20mL of Hydrochloric acid. After this step, we moved to the lab. We immediately got out our safety goggles and aprons, and applied them. Safety in the lab was our #1 goal. In the lab, we got a pipette, a beaker, and a graduated cylinder. We went to the Magnesium station and cut the Magnesium strips to exactly .24 grams. We measured this on the scales, using protective weighing paper. Next, we put on our goggles, and went to the Hydrochloric acid station. We poured slightly more than 20mL into our graduated cylinder, as Mr. Siegel had instructed. We then poured the Hydrochloric acid from the graduated cylinder into our beaker. When we were prepared at our stations, we dropped the solid magnesium into the beaker of Hydrochloric acid. We then observed and recorded our results.

What We Thought Would Happen: Our original thought was that this was going to be a warm fizzy, because that is what Mr. Siegel told us would happen, and it did. However, we also believed that we would be able to use exactly 20mL of Hydrochloric Acid to completely use and/or make a full reaction with the .24 grams of magnesium. We believed that if we just dumped all of the acid on top of the magnesium, then the reaction would occur on its own. We were wrong. What Actually Happened: When we conducted our experiment, we got a few extra milliliters of Hydrochloric Acid, to account for human error on our part. Apparently, we didn’t get nearly enough, for it took almost 29mL and over 35 minutes for the reaction to occur, and was still occurring as we left the lab. This was not part of our original plan. As well, we ended up stirring it in hopes of speeding up the reaction, which more or less worked. It did not, however, make it fast enough to completely react with the magnesium before the class time was over. Conclusion: After this experiment, we realized several things we did wrong, mostly because Mr. Siegel told us we did wrong. First of all, when inducing the reaction between the magnesium and hydrochloric acid, we should have poured the acid little by little on top of the magnesium, waiting for the reaction to completely occur each time before we added any more. This would allow us to determine exactly how much hydrochloric acid was actually needed to completely react with the magnesium, as we have no idea how much of the 29mL actually reacted with the magnesium. Second of all, we did not allow the reaction to finish, even though this was not really our fault and due merely to time constraints. But we realized some things about the experiment in retrospect. The hydrochloric acid was the limiting reactant in this reaction, for the reaction did not completely occur with the original amount we used. As well, the magnesium strips were weighed at .24 grams, but occasionally the scale would fluctuate, so we are not completely sure if our measure was accurate. If we were to do it again, then we would fix these grievous errors.