The precipitate partially dissolved as the ammonium hydroxide solution was

The precipitate partially dissolved as the ammonium

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white zinc hydroxide precipitate formed upon the addition of ammonium hydroxide. The precipitate partially dissolved as the ammonium hydroxide solution was added and a powder- blue solution was formed. An additional 5 mL of ammonium hydroxide was needed to dissolve all of the precipitate from the solution. Upon adding, the solution turned dark blue in color and was clear of any precipitates. The beaker was then left to cool to room temperature while a 100 mL volumetric flask was obtained and rinsed. After cooling to room temperature, the solution of copper (II) tetra ammonia complex was quantitatively transferred to the clean volumetric flask. The solution was then diluted with distilled water to the mark on the flask. The solution was then thoroughly mixed by inverting the flask several times until an observable homogenous solution was formed. The solution was then labeled as “Penny Solution” and then used to measure the absorbance at approximately 620.1 nanometers. In order to obtain the absorbance data, a spectrophotometer was connected to a computer where the appropriate absorbance program was installed. A cuvette was first marked, filled with distilled water, and then placed in the spectrophotometer device to serve as a blank for the data. The “Penny Solution” was then placed into the same cuvette after it had been rinsed and dried. Using the same orientation, the cuvette was placed in the spectrophotometer device where the absorbance was calculated and recorded. Five beakers were then obtained and thoroughly cleaned and dried. The beakers were 2070 – © Cornell University (2019)
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Copper in a Penny then labeled 1 through 5 using a dry erase marker. The first beaker was then used to obtain 15 mL of 0.04 M Cu(NH 3 ) 4 2+ . In order to prepare a series of solutions with a known concentration of Cu(NH 3 ) 4 2+ , serial dilutions were prepared using the five beakers. A volumetric pipette and bulb was obtained and properly cleaned to ensure exact measurements of the solutions. The pipette used to dispense exactly 10 mL of distilled water into the remaining four beakers that did not contain the 15 mL of 0.04 M Cu(NH 3 ) 4 2+ . The volumetric pipette was then used to dispense exactly 10 mL of the 0.04 M Cu(NH 3 ) 4 2+ solution into beaker #2 while a stirring rod was used to thoroughly swirl the mixture. Using the same procedure, the volumetric pipette was then used to dispense exactly 10 mL of the solution in beaker #2 into beaker #3 while a stirring rod was used to thoroughly swirl the mixture. The pipette was then used to continue to dilute the stock solution by dispensing exactly 10 mL of the solution in beaker #3 into beaker #4. The final dilution performed was by dispensing exactly 10 mL of the solution in beaker #4 into beaker #5. These
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