How Galvanized Is Your Washer?Catherine Lozier01/15/2013Chem 1310 Section C02TA: Ryan BucherLab Partners: Chelsey Arnold, Sunya Morin, Tran GHonor Pledge: I did not copy this work from any others student(s), current students in lab or old lab reports ________________________________________________SignatureDISCUSSIONA. The objective of part A is to use various methods to determine the thickness of the zinc coating on washers. The average mass of the master washer is 0.760g less than the given mass of 5.200g. Because thick zinc coating is associated with hot dipping, and the master washer had significantly less mass, it is likely that the master washer was electroplated. However, the average mass of the other washers was 5.229g, which is much higher than the master washer. Therefore it is likely that several of the washers measured were hot-dipped. The standard deviation of the masses used in the average was 0.7337, so it is likely that some of the washers were electroplated. Some sources of error would be the length of time we gave the reaction. When the washerwas removed, there were a few small spots of unreacted zinc remaining. This would skewthe zinc measurements and indicate a smaller zinc coating. Another source of error is the balances that we used to measure the washer masses. While taking measurements, the readings would often fluctuate within a range of around 0.010g. To compensate for this, the intermediate value was recorded; however this could have had a small influence on the accuracy of our measurements. B. The objective of part B was to use volumetric techniques to determine the average density of the washers. Data about the graduated cylinders were taken to get information on the precision of each cylinder. Based on the volume measurements, the density of the washers was calculated to be 8.12 g/cm3. This measurement is higher than the known density of zinc, 7.14 g/cm3. Any inconsistencies in measurements could be attributed to the lack of precision of the 100 mL graduated cylinder. Also, the cylinder’s measurementsmay have been inaccurate, in which case all of the recorded volumes would have a small systematic error. Another source of error is the human error in measurement. By visually gauging the volume in the cylinder, a certain degree of human error was introduced. While making the measurements, there was often some dispute as to the correct volume, as the meniscus often fell between two line markers. This could have also contributed error to our measurements.C. The objective of part C was to determine if the master washer is a USS washer or an SAEwasher. Based on the calculated zinc thickness of 0.07 mm, it is likely that the master washer was a USS type washer. Of course this classification is subject to the errors in measurements. There were likely human errors in taking the dimension measurements, aswell as possible systematic errors in the weight measurements.DISCUSSION QUESTIONS1. Weighing one washer on multiple scales yields a more accurate value for the mass of the washer, whereas weighing multiple washers on one scale will be less accurate, as any offset of the scale is reproduced in all measurements. However, the average mass of the washer was 0.760 g less than the stated value, which is a significant difference.2. If the washer had been removed before the reaction was entirely complete, not all of the zinc would have undergone a reaction. Therefore there would still be a thin layer of zinc on the washer in some areas. This would increase the measured mass of the washer after the reaction. A higher post-reaction mass indicates a thinner zinc coating on the washer prior to the reaction. This would not reflect the true thickness of the zinc coating on the washer.3. The 25 mL graduated cylinder was the most precise.4. The water displacement method was the most accurate means of estimating an average density for the washers because of the high sample size. The data included 30 washers, which would give a more accurate average measurement than a smaller sample size. The weight calculations were far more precise because it was possible to measure the weight to one thousandth of a gram. These measurements had far more significant figures, making them more precise than the water measurements.5. Because the master washer had a 10.8% mass percent difference from the stated true mass, it is likely that the washer was electroplated. The master washer has significantly less mass than the given true value, the zinc coating was thinner than expected. Because thinner zinc coating is associated with electroplating, it is likely that this was the method used to galvanize the washer.6. Based on the figure, the service life of the master washer is around 40 years in an industrial environment.REFERENCES1. American Galvanizers Association, “Zinc Coatings,” retrieved from www.galvanizeit.org,accessed January 15, 2013, http://www.galvanizeit.org.images/uploads/publicationPDFs/Galvanized_Steel_vs_Zinc_Spray.pdf2. Lab