Lab: Acids and Bases Many common household solutions contain acids and bases. Acid-base indicators, such as litmus and red cabbage juice, turn different colors in acidic and basic solutions. They can, therefore, be used to show if a solution is acidic or basic. Objective: In this experiment, you will use red cabbage indicator to determine the ph values of various household substances. Materials: Materials Household substances: (suggestions) well plate household cleaner shampoo distilled water wash bottle with distilled water ammonia ethanol tap water red cabbage juice lemon juice vinegar hydrochloric acid paper towel soft drink hydrogen peroxide pond water drain cleaner antacid tablet lemonade dishwasher detergent laundry detergent tea baking soda hand soap sodium chloride washing soda Pre-lab: You must complete the following before the lab day: Answer the Following Questions in your lab journal: 1. Based on your previous knowledge, predict which of the household substances you will be testing are acids/bases or neither. 2. What is the ph range for acidic solutions? [H 3 O + ]? 3. What is the ph range for basic solutions? [OH - ]? 4. If a solution is neutral what do you know about the ph? [H 3 O + ]? [OH - ]? In your lab journal, record the following: List all precautions that must be followed for this lab. Create a data table in your journal, using step 1 in the lab procedure as a guide. Do not record the names of the solutions yet. Write out the procedure. Lab: Acids and Bases 1 acid_base_lab_2015.odt
Precautions: Goggles and aprons must be worn at all times while you are in the lab area. Do not eat or drink in the laboratory. Ammonia solution is toxic. Its liquid and vapor are extremely irritating, especially to eyes. Drain cleaner solution is corrosive. Handle these solutions with care. Do not allow the solutions to contact your skin or clothing. Notify your teacher immediately in the event of an accident. Aprons and goggles must be worn at all times during this lab. Procedure: 1. Create a data table that has the cell numbers of the well plate (1A-6A, 2B - 6B, etc. ) along with space to record the name of the solution and all observations. Do not record the solution names yet, you can record them as you collect samples. See sample picture of the cell plate below, each square is a well where you will place your samples. 1A 2A 3A 4A 5A 6A 1B 2B 3B 4B 5B 6B 1C 2C 3C 4C 5C 6C 1D 2D 3D 4D 5D 6D 2. Following the instructors directions, rotate through each table, collecting samples of about 10 drops of each solution in a cell of your well plate. Make sure that you record the solution and location (cell #) in your well plate in your lab journal immediately. 3. Add about 10 drops of red cabbage juice indicator to each of the well plate cells. Record the color and use the color scale at your station to estimate the ph. Be sure to record all of this data immediately. 4. Rinse all solutions into the waste beakers with your wash bottle. Do not pour solutions into the sink. Rinse with the distilled water bottle and dry your well plate with paper towel. Leave your well plate at your assigned lab station. Lab: Acids and Bases 2 acid_base_lab_2015.odt
Questions for Lab: Acids and Bases Answer the following questions in your lab group. One paper per lab group. Submissions must be double spaced. Use the data collected to answer the following questions. 1. Create a table which lists all of the solutions tested from lowest to highest ph. Give the ph value of each solution. Classify each solution as acid, base or neutral. 2. Were there any solutions that were difficult or impossible to test for ph using the method in this lab? Explain why they were difficult or impossible to test. 3. Of all of the edible solutions that were tested, which ones had the lowest ph? Which ones had the highest ph? 4. Tooth enamel is made of the compound hydroxyapatite, which has the formula: Ca 5 (PO 4 ) 3 (OH) Do you think that hydroxyapatite is acidic, basic or neither? hint: Look at the formula. Although there are some food items that are fairly acidic, (with ph < 3.0) Dentists do not recommend eating these foods regularly. Explain why dentists would recommend that you don't eat highly acidic foods. Which of the edible solutions that we tested would you want to avoid for this reason? 5. Ethanol has the chemical formula: C 2 H 5 OH Hydrogen peroxide has the formula H 2 O 2. When you tested these solutions, did you find them to be acid, base or neutral? Were your findings consistent with the formulas of these compounds? Explain your answers. 6. Pure water has a ph of 7. Based on this, were your samples of water that you tested pure? If not, what may have accounted for it not being pure? Explain completely. 7. Evaluate this experiment. Include in your evaluation any difficulties that you encountered along with suggestions for improvements in the procedure. Lab: Acids and Bases 3 acid_base_lab_2015.odt
Red Cabbage Indicator Chart Lab: Acids and Bases 4 acid_base_lab_2015.odt
Lab: Acids and Bases 5 acid_base_lab_2015.odt