Lab 12: Alka Seltzer and the Ideal Gas Law

 In this lab, solid sodium bicarbonate (NaHCO3) and citric acid (C6H8O7) reacted with water (H2O) to produce CO2. We collected the CO2 that was given off and used it in the ideal gas law to determine the amount of gas produced. By using a balloon filled with Alka Seltzer powder and a test tube full of water, the powder reacted with the water to produce CO2 that inflated the balloon. Once the reaction ended, we measured the circumference of the inflated balloon and filled the balloon up with water until the water balloon had the same circumference as the gas balloon. We used the water volume in the ideal gas law to finally calculate the amount of CO2 in the balloon.

My Data Table

My Calculations

CO2 inflating the balloon

Analysis Questions:
1. There are multiple areas experimental error may have occurred. For example, we could have inaccurately measured the circumference of the CO2-filled balloon or we could have dropped some powder while transitioning it from the mortar to the balloon. I also know that some water escaped the balloon as we were trying take it off the sink head and pour it into the graduated cylinder.

2. If water leaked out from the balloon, the recorded volume of the balloon would be smaller than the actual volume of the balloon. Since volume has a direct relationship with mass according to Avogadro's law, the number of moles ("n") of CO2 would be too small.

3.  38.00cm= 2πr --> r=6.05cm; V=4/3π (6.05cm)^3= 926.6cm^3= 926.6mL

4. The two volumes (experimental and calculated) of the balloon appear close. I feel that the experimental volume of the balloon is more accurate than the calculated volume because the shape of the balloon is not a perfect sphere. Although some human error may have effected the final numbers of the experimental volume, it is still more accurate than the calculated volume of the balloon.

5. Real gas molecules have interactive forces such as repulsion and attraction while ideal gases aren't supposed to have any interactive forces according to the kinetic molecular theory of gases. This theory also states how ideal gases should not lose energy from collisions with objects or other gas particles, but real gases do not have elastic collisions and tend to lose energy in any collision.

6. The CO2 in this lab would not be considered an ideal gas because ideal gases don't exist and it takes up mass and volume.

Advanced Questions:
1. Each tablet had 1000 mg of citric acid (C6H8O7) and 1916 mg of baking soda (NaHCO3). Using three Alka Seltzer tablets, we found that 3g of citric acid produced 2.062 g of CO2 while 5.74g of baking soda produced 3.011 g of CO2. Since citric acid was the limiting reactant, the theoretical yield is 2.062 g CO2.

2. 1.86g CO2/ 2.062g CO2= 90.2%

3. Some of the CO2 may have been dissolved in the water and therefore was not measured in the balloon as part of the gas volume. This explains how out calculated amount of CO2 appeared higher than our actual amount of CO2 obtained.