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Gravimetric Analysis of a Chloride Salt Short Report Date submitted: By: Lab section: Group: TA:

Procedure: Weighing the salt samples by difference: 1. The vial of salt sample 337 was placed into the analytical balance and the balance was zeroed to measure the mass of salt content removed. 2. A small amount of salt was removed from the vial and placed into a 250.00 mL beaker and the vial was placed back into the balance. 3. The mass salt removed from the vial was deduced from the zeroed value on the analytical balance. 4. The process was repeated until a sample value of about 0.1000 g to 0.1500 g was collected into each of the two 250.00 mL beakers. a. In this particular experiment, 0.1306 g ± 0.0001 g of salt sample 337 was measured and collected into beaker 1 and 0.1015 g ± 0.0001 g was collected into beaker 2. Preparation of solution: 1. Both 250.00 mL beakers were filled to approximately 100.00 mL with distilled water and the solutions were stirred with a glass rod. 2. 1.00 mL of HNO 3 was added into each solution and stirred. 3. Using the calculated masses, the volume of AgNO 3 required for each salt sample was calculated and added to its respective solution from a 100.00 mL beaker using a 50.00 mL graduated cylinder. 4. The solutions were mixed with a glass stir rod. Precipitation test and storage: 1. Each salt sample was placed on a hot plate which was turned onto medium heat, making sure the solution did not boil. 2. Each sample was stirred occasionally, without removing the glass stir rod. 3. A few drops of AgNO 3 were dropped into each salt sample to test for completion. a. If too cloudy or precipitate formed, then supernatant remained on hot plate until no precipitate formed. 4. Once passed the precipitation test, the beakers were removed from the hot plate and placed into a drawer until cooled. Filtration and washing of the precipitates: 1. Without folding, a piece of filter paper was placed into each of the two 50.00 mL beakers and then massed using the analytical balance. 2. The filter paper from beaker one was inserted into one of the Buchner funnels of a vacuum filtration apparatus and soaked with distilled water. a. The same was done for filter paper number 2 in the second funnel. 3. Once the water had passed through, the supernatant liquid for beakers 1 and 2 were decanted through their respective funnels. 4. To wash the precipitates, several mL of 0.01M HNO 3 was decanted through the precipitates and the filters a total of three times.

5. After stopping the vacuum, the waste filtrates were thrown out and the apparatus was then reassembled and turned on. 6. Another several mL of HNO 3 were poured over the precipitates in the Buchner funnels. Once the acid had passed through, the vacuum was stopped and unassembled again. 7. Several mL of the washing was poured into two separate test tubes, making sure to not fill them completely, and 3 drops of HCl were pipetted into the tubes to test for completion of wash test. a. If any cloudiness was visible in the tubes, steps 1-7 in the washing procedure were repeated until the washings remained clear. 8. The contents of the test tubes were discarded into the sink and the tubes were cleansed with distilled water. Excess wash from the filter glasses were also discarded in the sink. 9. Once the vacuum was reassembled and turned on, the precipitates were covered with acetone. Once the liquid had passed through, this process was repeated 2 more times. 10. Once the precipitates were dry, the vacuum was turned off and the apparatus was disassembled. The acetone glasses were then disposed of in their respective container. Drying and massing of precipitates: 1. Over a piece of paper towel, the filter papers were carefully removed from their funnels using a micro spatula and transferred into their respective 50.00 mL beakers, making sure all solids went into the beaker. 2. Each 50.00 mL beaker was placed into an oven at 86.0 °C for 13 minutes. 3. After the samples had cooled for 4 minutes, each beaker with its precipitate and filter paper was massed using the analytical balance. 4. Once values were measured, the filter papers and precipitates were disposed of and all instruments were thoroughly cleaned using distilled water. Data and Observations: 1. Once the AgNO 3 was added to the solutions, they became a cloudy, opaque white. a. Grey precipitate formed in the solutions instantly. 2. If the samples failed the precipitation test for completion, grey, clumpy matter would form in the solution. 3. Several grams of precipitate filtered through the vacuum while the washing test was being conducted. 4. A small amount of precipitate was left stuck to the 250.00 mL beakers and the Buchner funnels, unable to be rinsed or scraped off into the final massed samples. 5. The temperature of the oven quickly rose from 80.0 °C to 86.0 °C within 3 minutes of placing the 50.00 mL beakers inside. The temperature remained relatively consistent throughout the rest of the drying process. • Table 1: Initial and final description of the physical changes of each sample Sample Initial Physical Description (salt) Final Physical Description (precipitate)

Number 1 - White, grain-like powder - White, grain-like powder 2 - Clumped light purple powder - Clumped light purple powder • Table 2: Representing the check for completeness of each test per sample Sample Number Completeness of Precipitation Test Completeness of Washing Test 1 - No additional AgCl formed - Translucent solution - Cloudy, white precipitate forms on first wash - No turbidity observed after second wash 2 - Precipitate formed quickly in clouded solution - No additional AgCl formed on the second trial - No turbidity observed • Table 3: Data of the weight of the samples and precipitates Sample Number Mass of Salt Sample 337 (±0.0002 g) Mass of the Beaker with Filter Paper (BF) (±0.0002 g) Mass of the Beaker with Filter Paper and the Precipitate (BFP) (±0.0002 g) Mass of the Precipitate (±0.0004 g) 1 0.1306 29.79 29.96 0.1716 2 0.1015 28.90 29.16 0.2596 • Table 4: Data of the oven temperature (in degrees Celsius), drying time (in minutes), and cooling time (in minutes) Sample Number Oven Temperature ( °C) Drying Time (mins) Cooling Time (mins)

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