SOUR STOMACH:

WHICH ANTACID IS MOST EFFECTIVE?

Antacids are medications that are used to treat “heartburn” or excess acid in the stomach. Pharmaceutical companies promote their products, such as Alka-Seltzer or Tums as fastest and most effective in reducing stomach pain associated with this problem.

In this lab activity you will simulate stomach acid using lemon juice and water and then test three different heartburn relief products for their effectiveness in neutralizing the acid in your model “sour stomach”.

Recall that on the pH scale, neutrality is represented by a 7. A pH below 7 is acidic, and the lower the number the stronger the acid. A pH above 7 is basic or alkaline, and the higher the number the stronger the base. Also, remember that pH values are logarithmic.

Write up this lab activity as you usually do, including all required components.

You will use your CBL-Calculator set-up with a pH probe to monitor the neutralization process when you add each of the antacids to your model stomach. You must set up your equipment to Time Graph the pH every .5 seconds for a total of 120 readings and then print your graph and data list for each of the products. You will then compare your results with the rest of the class.

Create your “stomach” by placing 125 mL of distilled water in a very clean 250-mL beaker and placing the pH probe in the beaker. (It is essential that you carefully rinse the probe with distilled water each time your use it!) Add 20 drops of lemon juice to the water, noting the original pH, and start the time graph. Quickly add the first antacid and stir with the probe until the graph is complete. Print your graph and data lists, making sure to label appropriately. Archive your lists for later use. Repeat this procedure for two other antacids.

Exit the CBL application and create a graph with all three curves on the same screen.

Answer the following questions.

1. Are all of the graphs exactly the same?

2. What do you conclude about the effectiveness of the antacids? Explain your reasoning.

3. What factors might have affected your results?

4. How could you eliminate some factors that might have reduced the antacid’s effectiveness?

5. What chemicals might be used in manufacturing antacids?

6. Are your results similar to those of the rest of the class?