Page 1 of 3 All That Fizz: CO2 Gas PASPORT CO2 Gas Sensor (PS-2110) ScienceWorkshop CO2 Gas Sensor (CI-6561 - Available Jan 2003) Purpose: Students will measure the amount of CO2 gas produced during a chemical reaction of Alka-Seltzer tablets with water. Background Information: Alka-Seltzer neutralizes the acids in the gastrointestinal system by combining with hydrochloric acid in the stomach to form a salt and water. We learned that an endothermic reaction occurs, causing the temperature of the water to decrease. Alka-Seltzer contains both citric acid (C6H8O7 - anhydrous) and sodium bicarbonate (baking soda - NaHCO3). When you drop a tablet in water, the acid and the baking soda react, producing the famous fizz we see. The bubbles, or fizz, is the result of CO2 being produced. Hypothesize: What effect does the number of Alka-Seltzer tablets have on the rate of reaction and CO2 change? Equipment and Supplies: For each lab group: CO2 Gas Sensor: PASPORT (PS-2110) Computer Interface PASPORT Xplorer (PS-2000) | (3) Alka-Seltzer tablets (2) 250-mL beakers Tap Water Page 2 of 3 Software and Probeware Setup: 1. Ensure that your USB Link, Xplorer is connected to the computer.. 2. When the file is opened, you should see a Graph Display of CO2 vs. Time, as well as a Digits Display of CO2. 3. Connect the CO2 Sensor to the Xplorer. 4. Resize and arrange the displays as needed so that you can see them all. Experimental Procedure Data Collection & Recording: 1. Pour 100 mL of water into each beaker. 2. Position the CO2 Gas Sensor above the first beaker of water, securing with a clamp if necessary. CAUTION! Do not get the probe wet! Click the Start button ( ) to begin collecting data. 3. While holding the CO2 Gas Sensor nearby and above the first beaker, drop one Alka-Seltzer tablet into the beaker. 4. Monitor the CO2 gas that is generated for several minutes until no further change is observed, then click the Stop ( ) button to end data collection. 5. Record the starting and ending CO2 levels in your data table. 6. Record any additional observations about the progress of the reaction in your data table. 7. After completing steps 3-6, repeat the same procedure using the second beaker and 2 tablets. Data Analysis: 1. Examine the Graph Display to view your data, using the Scale to Fit button ( ) in the Graph toolbar to resize the axes as needed. 2. Use the SmartTool ( ) to pinpoint the starting and ending CO2 levels for each reaction. Record this information in your data table. Page 3 of 3 3. Compare the two runs and observe the differences in CO2 extremes and any variations in the rate of reaction. Sample Data Table: CO2 (1 TABLET) Observations: CO2 Data: (ppm) Start of Reaction: End of Reaction: ppm for reaction: _____ 4. CO2 (2 TABLETS) Observations: CO2 Data: (ppm) Start of Reaction: End of Reaction: ppm for reaction: _____ Conclusions and Extensions: 1. What happened to the CO2 levels in the first reaction? Is this evidence of a physical change or a chemical change? 2. What happened to the CO2 levels in the second reaction? 3. Is there a correlation between the rate of reaction and the number of tablets used? Why?