Chemical Change – Reaction between stomach acid and antacid

A wide variety of chemical reactions occur in our own bodies. For the treatment of heart burn, many people rely on commercial antacids. In this exploration, we will simulate the reaction that happens in your body when you take an antacid and study energy changes associated with reaction between antacid and stomach acid. As 0.36 M HCl is a good approximation for stomach acid, we will be using this solution as our model.

Materials: Styrofoam cup and lid to build a calorimeter, two antacid tablets, mortar and pestle, 0.36 M HCl, thermometer, stir bar and stir plate

Method:

Remove the lid/thermometer of the calorimeter and add 50 ml of 0.36M HCl.

Turn on the stir plate and set at a low setting (about 3).

Wait for the temperature of the 0.36 M HCl to stabilize and record the temperature. 

While waiting for the temperature to stabilize, crush two tablets of antacid using a mortar and pestle.

Open the lid of the calorimeter wide enough to add your crushed tablets. Put the lid back immediately after the addition of the antacid.

1.      Once the temperature stabilizes, record the temperature.

2.      Transfer your temperature data to Table 1.

3.      Dispose of contents of calorimeter as instructed by instructor and rinse all parts of the calorimeter.

4.      Calculate the difference in temperature and complete Table 1.

Result:

Temperature of HCl = 25.1 °C

Temperature after addition of Tums =  31.9 °C

Conclusions

Write the results in the table 1 and calculate difference in temperature.

Table 1:

Reaction

Initial Temperature

Final Temperature

Change in Temperature= Final temperature-Initial temperature

PHYSICAL CHANGE

NaOH in DI water

25.1

33.1

1 M KCl in DI water

25

24.9

CHEMICAL CHANGE

Liquid NaOH and HCl

25.1

31.9

Tums and acid

25.9

26.6

Questions:

1.      Which of the reactions were exothermic in nature and which were endothermic?

2.      From the previous experiments, if you heated the water, would this alter their exothermic or endothermic behavior?

3.      What was the reason that you needed to wait for the temperature to stabilize?

4.      A chemical reaction requires more energy to break bonds than the energy released from the formation of new bonds. What would I classify this reaction as?

5.      When you leave a cold bottle of soda out on a warm humid day, water begins to condense on the surface of the bottle. Describe what is happening in terms of energy change.