The Sequence Of Chemical Reactions Essay Research

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The Sequence Of Chemical Reactions Essay, Research Paper The Sequence of Chemical Reactions Drew Selfridge Dave Allen, Lab partner Instructor Yang February 11, 1997 INTRODUCTION This experiment was to recover the most amount of copper after it is subjected to a sequence of reactions. The copper is originally in solid form, but the reactions will turn it into free Cu+2 ions floating in solution. The ions will then be regrouped to form solid copper once again. During this process, however, some of the Cu+2 ions may be lost. The copper will subjected to changes in pH and heat. These steps were responsible for the breakdown and reconstruction of the copper. The percent of copper retrieved will reflect the skill with which the reactions were administered. EXPERIMENTAL On an

analytical balance, measure the mass of the copper while in the vial. Remove approximately 0.35 g into a 250 mL beaker. check the balance and record the mass of the remaining mixture in the vial. In the laboratory hood, dissolve the copper with ~ 3 mL of nitric acid. Allow the beaker to remain under the hood until the fumes cease. The remaining solution should be blue. Bring the beaker back to the lab station and add ~ 10 mL of distilled water. Stir the mixture, all the while adding ~ 8 mL of 6M of NaOH to the beaker. Check with litmus paper to ensure that it is slightly basic. Fill the beaker with up to 100 mL mark with distilled water. Heat the solution and allow it to boil for 5 minutes. Prepare a squirt bottle with hot water. Filter the solution and rinse the beaker with the

hot water. Rinse the filter cake with hot distilled water. Transfer the filter paper into a clean beaker. Add ~ 10 mL of 3M sulfuric acid to the beaker in order to dissolve the filtrate. Remove and rinse the filter paper. Now add ~ 0.35 g of zinc powder to the solution and stir until the solution becomes clear. Dissolve the excess zinc with more sulfuric acid. Decant the liquid with a stirring rod, retaining only the copper. Rinse the copper with distilled water and steam dry. Weigh the mass. DATA/RESULTS initial mass of copper (g)0.319 final mass of copper (g)0.305 % recovery = (final mass/initial mass) x 100 95.6 OBSERVATIONS -between steps 1 through 4 the solution is blue. -between steps 5 through 8 the solution is dark brown. -between steps 9 through 12 the solution is

blue-green. -between steps 13 through 16 the Zinc turns red as the blue color slowly leaves the solution. CALCULATIONS % Recovery = (final mass / initial mass) x 100 % Recovery = (0.305 - 0.319) x 100 % Recovery = 95.6% CONCLUSION (a) The overall yield of the reaction was 95.6%. There may have been copper lost in transfer from beaker to beaker or stuck to the stirring rod while the copper was in the ionic state. The solid copper may have been lost in the filter paper or in the decanting of the liquid. The majority of the copper lost was probably lost when the copper was transferred from beaker to beaker or during the recanting of the liquid. The filter paper and stirring rod probably account for a small fraction of the copper lost. (b) The class average for the experiment was

96.11%. Based on this average our results were very precise to 0.5% The hypothesis would be that 100% of copper could be recovered there for our results were also accurate to 4.39%. (c) The hypothesis was supported by the experimental results because two groups recovered 100%. (d) Our results were less then the class average. This explained by possilbe loss of copper when transferring between different stages of the experiment. (e) Buring of the copper during the drying stage would be a systematic error that would result in a class average greater than 100% yield of copper.