SURVEY OF CHEMISTRY LABORATORY I CHEM 1151L ANTACID EVALUATION

CAUTION!!! BE SURE TO WEAR SAFETY GLASSES AT ALL TIMES IN THE LABORATORY NO EXCEPTIONS TO THIS RULE!

- To compare commercial preparations (antacids) commonly used to combat acid indigestion - Students will react three different antacids with excess HCl acid - A portion of the acid will be neutralized by the antacids - Amount of unreacted acid will be determined by titration with NaOH base - The least neutralized sample by antacid will require most base ANTACID EVALUATION

- Acid indigestion or heartburn is a common malady in our daily life - Results from foods and drinks - The normal functioning of the stomach in the digestive process requires that acid be present - Stomach acid (called gastric juice) is hydrochloric acid (pH ≈ 1.0) - A prolonged or recurring condition of indigestion may lead to damage of the stomach lining and result in ulcers - Antacids are basic and used to neutralize stomach acid ANTACID EVALUATION

- An indicator is required to see when enough base has been added to the acid - Phenolphthalein indicator will be used in this experiment - Phenolphthalein is colorless in acidic solutions and pink in basic solutions - End point of titration is reached when solution turns into faint pink upon addition of NaOH - This implies all acid is neutralized by base INDICATOR

- Obtain 4 clean 125 mL Erlenmeyer flasks 4 ERLENMEYER FLASKS

- Use a buret to measure mL of 1 M HCl into each of the 4 Erlenmeyer flasks MEASURE HCl ACID

- Use a buret to measure mL of 1 M HCl into each of the 4 Erlenmeyer flasks MEASURE HCl ACID

- Select 3 antacid tablets - Grind each tablet into powder using the mortar and pestle - Mass each tablet with a different weighing paper - Place each in separate flasks and label them - Also mass ~ 0.5 grams of baking soda NaHCO 3 into the fourth flask - Be sure to label the flasks PREPARE ANTACID SAMPLES

- Select 3 antacid tablets - Grind each tablet into powder using the mortar and pestle - Mass each tablet with a different weighing paper - Place each in separate flasks and label them - Also mass ~ 0.5 grams of baking soda NaHCO 3 into the fourth flask - Be sure to label the flasks PREPARE ANTACID SAMPLES

- Select 3 antacid tablets - Grind each tablet into powder using the mortar and pestle - Mass each tablet with a different weighing paper - Place each in separate flasks and label them - Also mass ~ 0.5 grams of baking soda NaHCO 3 into the fourth flask - Be sure to label the flasks PREPARE ANTACID SAMPLES

- Select 3 antacid tablets - Grind each tablet into powder using the mortar and pestle - Mass each tablet with a different weighing paper - Place each in separate flasks and label them - Also mass ~ 0.5 grams of baking soda NaHCO 3 into the fourth flask - Be sure to label the flasks PREPARE ANTACID SAMPLES

- Make sure each antacid is completely dissolved - Add 3 – 4 drops of phenolphthalein indicator to each flask PREPARE ANTACID SAMPLES

- Rinse your buret with about 3 – 5 mL of 0.5 M NaOH solution - Fill the buret with the 0.5 M NaOH solution - Use small beaker to fill (do not use funnel) FILL BURET WITH NaOH

- Drain some NaOH to fill the tip - Record the initial reading FILL BURET WITH NaOH

- Place one of the flasks under the buret and begin to titrate - Allowing the NaOH to drip steadily into the flask - Swirl flasks continuously - Be careful not to go over the end point (over titrate) TITRATE SAMPLES WITH NaOH

- Pink color will begin to appear and disappear after swirling - Add one drop at a time at this point - Stop when pink color remains for at least 30 seconds (end point is reached) - Read and record the final reading - Do not go past the 50 mL mark (stop and refill if necessary TITRATE SAMPLES WITH NaOH Click on picture to play video

- Repeat procedure for each of the remaining flaks - Determine the volume of NaOH used for each flask - Calculate the efficiency number for each tablet using the equation below (include appropriate units) - Also record the active ingredients for each tablet from their bottles DETERMINE EFFICIENCY NUMBER