SURVEY OF CHEMISTRY LABORATORY I

CHEM 1151L

ANTACID EVALUATION

CAUTION!!!CAUTION!!!BE SURE TO WEAR SAFETY GLASSES AT

ALLTIMES 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 25.00 mL of 1 M HCl into each of

the 4 Erlenmeyer flasks

MEASURE HCl ACID

- Use a buret to measure 25.00 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 NaHCO3 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 NaHCO3 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 NaHCO3 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 NaHCO3 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

Sample) of (Mass

Used)NaOHVolume(50.00NumberEfficiency

DETERMINE EFFICIENCY NUMBER