Chem. 253 Lab 1: Acid/Base Properties of an Antimicrobial Agent 09/03/13 Purpose The purpose was to determine the acid and base properties of the antimicrobial agent sodium beneath. Theory Sodium has mainly been used in food processing to avoid growth of bacteria and harmful microorganisms. It is commonly used to preserve foods and beverages that have an acidic PH. Rather than benzene acid, sodium beneath is used because it is generally soluble in most aqueous solutions but benzene acid is not. Reaction
Sodium beneath mixed with water, dissociates into beneath and sodium ions. Hydrogen chloride, which is a gas, will exist in unionized form when combined with water to form hydrochloric acid. Then when the two solutions are combined, HUH+ transfers electrons to beneath ions, which act as the base to form benzene acid as a solid precipitate. The overall balanced equation is as follows. Yield Calculations: Sodium Beneath: Theoretical: The theoretical yield of Benzene Acid is 1. Egg. The actual yield of Benzene Acid is 1. Egg.
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The percent yield of this experiment is: Methods/Procedures 1) Weigh and tare a 50 ml beaker, then place about 1. G of sodium beneath into the beaker. Record the actual mass of sodium beneath used. 2) Measure about 10 ml of distilled water with a graduated cylinder and pour it into the beaker with the sodium beneath. Use a glass-stirring rod to dissolve the sodium beneath in the water. 3) Measure about 4 ml of 3. 0 M HCI and add it slowly, with stirring, to the sodium beneath solution until the pH of the solution is 2.
Use pH paper to test the solution each time by using your stirring rod to place a drop of the solution on the pH paper. Adding excess HCI to the solution will not affect yield of product. 4) To induce crystallization of product, cool the solution to 10 degrees Celsius or below. Place your 50 ml beaker in a large beaker containing cracked ice with a little water to reduce the temperature. 5) Clamp a 250 ml filtering flask to a ring stand and place the Boucher funnel on top with an appropriately sized filter paper (be sure to pre-weigh the filter paper).
Moisten the filter paper in the funnel with a little distilled water, and make sure that the moist filter paper fits snugly in the bottom of the Boucher funnel with no folds or bends in the filter paper visible. Use the thick rubber tubing from your drawer to provide vacuum from the “aspirator” to your “filter flask. ” Be sure you are connecting the tubing to the “aspirator,” not to the water or gas outlet. Turn on the water to a low volume to create a vacuum in the filter flask but not so much that you flood the sink. Transfer the crystals (quantitatively) from Step 4 to the funnel. Use about 5 ml of distilled water to rinse any solid that remains in the beaker onto the filter paper. Let the solid air-dry with the aspirator running for a few minutes. 7) Place the filter paper with solid in the oven for about 15 minutes to dry. Weigh and then dry again for 5 minutes. Weigh again. If your second weight differs from the first weight by more than 0. 5%, dry again for 10 minutes. Continue this process until successive weighing are within 0. 5%.
For this lab, we must be sure to always wear our safety glasses whenever we are in the laboratory and wear gloves when we are conducting an experiment. Benzene acid and sodium beneath used in this experiment can be mild irritants to the skin. We must be careful not to get them on Observations/Results The mixture began clear but once we added the HCI the substance was white and odorless. Our precipitate was solid and white. For the numbers, sodium beneath was the limiting reagent because it had 0. 01063 moles whereas hydrochloric acid had 0. 012 moles. The theoretical yield was 1. Egg and the actual yield was 1. 51 g. With these numbers the percent yield turned out to be 96. 37%. Discussion/Conclusion Throughout the experiment I felt as though there were some errors. Also, I feel as though I may have lost amounts of the mixture and precipitate through transfers that affected our final weight. I could tell that the pH had an effect because we know that if there is a decrease in pH a precipitate starts to form. Exercises 1) In a solution containing aqueous sodium beneath, a decrease in pH usually results in the formation of a precipitate. A.