Chem lab 2 - LAB REPORT PDF

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RED CABBAGE PH INDICATOR October, 2019 Peter Isibor K00402310 Chem 3123

Abstract

In this experiment a pH indicator using the anthocyanidin compounds in red cabbage will be made. A colorimetric pH indicator is a chemical compound added in small amounts to a solution, so the pH of the solution can be determined visually. These indicators are frequently employed in titrations in analytical chemistry and biology. Anthocyanins can be employed as colorimetric compounds because they change color at different pH values. The anthocyanidin motif exhibits subtle structural changes dependent on fluctuation in pH. In an acidic environment with a pH less than 7 the compound takes on the form. While in a neutral environment with a pH equal to 7 it is purple. Because of these color changes at different pH values, it is possible to determine the pH of a solution based on the color that this indicator turns. pH indicators such as anthocyanidin are added to solutions in minute quantities because it exhibits strong chromophores to begin with. This quality along with the ability to achieve structural change at different pH values establishes them as superior colorimetric pH indicators. In plants, anthocyanins are found in many flowers and fruits of plants and may serve a protective role against extreme temperatures. The absorbance pattern responsible for the red color of anthocyanins may be complementary to that of green chlorophyll in photosyntheticallyactive plant tissues.

MSDS 1.0 Hydrochloric Acid Chemical Formula: HCl Health: 2 Flammability: 0 Reactive: 0 Immediately flush eyes with excess water for 15 minutes, if inhaled remove to fresh air 36.46 g/mol, Clear liquid, Pungent odor 1.0 Acetic Acid Chemical Formula: CH3COOH Health: 2 Flammability: 0 Reactive: 0 Immediately flush eyes and skin with excess water for 15 minutes 60.05 g/mol, Clear liquid, Vinegar smell Ascorbic Acid Chemical Formula: C6H8O6 Health: 0 Flammability: 0 Reactive: 0 Rinse/flush exposed skin and eyes gently with water for 15-20 minutes. Remove to fresh air White crystalline powder, odorless Sodium Bicarbonate Chemical Formula: NaHCO3 Health: 2 Flammability: 0 Reactive: 1 84.01 g/mol, white crystalline powder, odorless 1.0 M Ammonia Chemical Formula: NH3 Health: 1 Flammability: 0 Reactive: 0 Immediately flush eyes and skin with excess water for 15 minutes Colorless liquid, Ammonia odor Sodium Acetate Chemical Formula: C2H3O2Na Health: 1 Flammability: 1 Reactive: 0 Immediately flush eyes and skin with excess water for 15 minutes 82.03 g/mol, White solid, odorless to slight acetic-like odor Procedure Obtain 10-15 grams of red cabbage and wash. Tear the cleaned red cabbage leaves into small pieces and place them into a large beaker with 150 ml of deionized water. Over a hot plate, boil the solution while occasionally stirring. Allow the solution to boil until the water is a dark purple. Once it has attained this color, carefully remove the beaker from the hot plate using tongs and allow the solution to cool. Note that if the solution turns green or blue instead of dark purple a clean beaker wasn’t used and/or

deionized water wasn’t used. In this case, attempt the procedure again more diligently. After extracting the anthocyanidins into the water, remove the solid cabbage pieces via vacuum filtration using either a Buchner or Fritted Funnel vacuum filtration. Make sure to use a course frit for the fritted funnel if employing this method of filtration. For this experiment we are interested in keeping the liquid and discarding the solid remains into the trash. Label seven test tubes with the following information and place them in a test tube rack. Be sure to add the specific amount described to each test tube and place them in a test tube rack, using a 10 ml graduated cylinder for precision being sure to read to the bottom of the meniscus. Employ an analytical balance for weighing the solids. To each test tube ad 3 ml of the red cabbage extract. Make sure to stir each solution with a glass rod to ensure complete dissolution and consistency with color throughout the test tube. The acid-base reaction between the chemical compounds and the anthocyanidins in the cabbage juice occurs very rapidly. Describe detailed observations of color changes in the lab notebook. Using rubber stoppers, thoroughly mix the 5 ml of 1.0 M acetic acid with the 0.41 grams of sodium acetate. Add 3 ml of the red cabbage extract to test tubes 8 and 9. Be sure to swirl the test tubes to mix thoroughly and record the observations. Next add 3 drops of 12.0 M Hydrochloric acid to both test tubes. Test tube 8 should have changed color within the addition of a few drops of the HCl. Test tube 9 should require more HCl before a color change is noted. Continue to add the 12.0 M hydrochloric acid 3 drops at a time to test tube 9 until a distinct color change is seen. Record observations. Do not add more than 30 drops Data Test Tube No. and Substance 1.0 M Hydrochloric acid 1.0 M Acetic Acid Ascorbic acid (Vitamin C) Nothing (non buffer) Sodium Bicarbonate ( Anhydrate, Carbonate) 1.0 M Ammonia Control # 4 + Di H2O 1.0 M Acetic Acid + Sodium Acetate

Amount 1 ml 1 ml .111 g N/A .108 g

Color Pinkish red Pink Hot Pink Purple Olive Green

1 ml 5 ml 5 ml + 0.41 g

Green Lavender Light Pink; 8 drops

Calculations None for this lab Conclusion Once 10-15 grams of red cabbage was obtained and washed, the red cabbage was torn into small pieces and placed into a large beaker with 150 ml of deionized water. The large beaker is then put onto a hot plate and the solution is then brought to a boil. The solution is boiling until the water is a dark purple color. Once the dark purple color is reached the beaker is carefully removed from the hot plate and allowed to cool. Then 8 test tubes are labeled, and the specific amount of each compound/chemical is put into its designated test tube. In test tube one, 1 ml of 1.0 M Hydrochloric acid mixed with the red

cabbage juice turned a pinkish red. In test tube two, 1 ml of 1.0 M Acetic Acid mixed with the red cabbage juice turned Pink. In test tube three, 0.111 g of Ascorbic acid mixed with the red cabbage juice turned Hot Pink. In test tube four, the red cabbage juice was put in the test tube because it was the nonbuffer and since it was only the red cabbage juice in the test tube it was Purple. In test tube five, 0.108 g of Sodium Bicarbonate (Anhydrate) mixed with red cabbage juice turned an olive-green color. In test tube six, 1 ml of 1.0 M Ammonia plus the red cabbage juice turned green. In test tube seven, the control (test tube 4) plus 5 ml of distilled water turned lavender. In test eight, 5 ml of 1.0 M Acetic Acid and 0.41 g of sodium Acetate was mixed with 3 ml of the red cabbage extract it turned a light pink with 8 drops of HCl. Observations were recorded. References Organic Chemistry I Chem 3123 laboratory Manual Jason Abrams Pre-Lab Questions

1.

2. Coumarin

3. 4.

Isocoumarin

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Chromone

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