Lab 18
Alka Seltzer and the Ideal Gas Law
Shiva Senthil
8/1/17
Introduction
The purpose of this lab was to calculate how much gas was produced in a chemical reaction. Alka seltzer powder was mixed with water to produce carbon dioxide, which was collected in a balloon.
Data
Calculations
Questions
1. Discuss an area in this lab where experimental error may have occurred.
Errors could have occurred in measuring the alka seltzer's mass, the measuring of the circumference of the balloon, and filling the balloon to the same circumference with water.
2. Choose one error from above and discuss if it would make "n" the number of moles of CO2 too big or too small.
While measuring the mass of the alka seltzer, the whole alka seltzer powder was measured. It was nearly impossible to scoop all of the alka seltzer into the balloon. Since there would be less alka seltzer than you would expect, the moles of CO2 would be too small.
3. Using the value for the circumference of the balloon in cm, calculate the volume of the balloon mathematically.
Using 2πr for circumference and 4/3πr^3 for volume of the sphere, we can solve for the volume using the measured circumference of 31.5cm. 31.5 = 2πr → r = 5.01cm. V = 4/3πr^3 → V = 527cm^3
4. Compare your answer to #3 to the volume obtained by filling the balloon with water. Is it close? Which is more accurate and why?
The mathematically calculated value is much lower. Filling the balloon with water is probably more accurate because the shape of the balloon is not exactly a sphere. The circumference measured was shorter than it would have been if the balloon had been a perfect sphere (the measurement was made where the balloon was thinner). Thus, a mathematical calculation would be smaller than the actual value, and filling the balloon up with water until it is about the same size is a more accurate representation.
5. The ideal gas law technically applies to ideal gases. Give two differences between a real gas and an ideal gas.
Real gases actually have a volume, while ideal gases are assumed to have particles infinitesimally small. Real gases also do not have elastic collisions like ideal gases do.
6. Would the CO2 you collected in this lab be considered ideal? Why or why not?
The CO2 would not be ideal because gases will behave ideally only when the temperature is very high and the pressure is very low (this allows the particles to move without being restricted and are less likely to be affected by intermolecular forces, which can cause collisions to transfer energy).
Advanced Questions
1. Using info from the label, calculate the mass of CO2 that should be collected per tablet.
2. What is the percent yield?
3. CO2 is water soluble. The solubility around room temperature is around 90mL/100mL of water. What effect does this have on your calculated n value?
This means that not all of the CO2 went in to the balloon as some was dissolved in water. Thus the n value was smaller than expected.
Calculations
Questions
1. Discuss an area in this lab where experimental error may have occurred.
Errors could have occurred in measuring the alka seltzer's mass, the measuring of the circumference of the balloon, and filling the balloon to the same circumference with water.
2. Choose one error from above and discuss if it would make "n" the number of moles of CO2 too big or too small.
While measuring the mass of the alka seltzer, the whole alka seltzer powder was measured. It was nearly impossible to scoop all of the alka seltzer into the balloon. Since there would be less alka seltzer than you would expect, the moles of CO2 would be too small.
3. Using the value for the circumference of the balloon in cm, calculate the volume of the balloon mathematically.
Using 2πr for circumference and 4/3πr^3 for volume of the sphere, we can solve for the volume using the measured circumference of 31.5cm. 31.5 = 2πr → r = 5.01cm. V = 4/3πr^3 → V = 527cm^3
4. Compare your answer to #3 to the volume obtained by filling the balloon with water. Is it close? Which is more accurate and why?
The mathematically calculated value is much lower. Filling the balloon with water is probably more accurate because the shape of the balloon is not exactly a sphere. The circumference measured was shorter than it would have been if the balloon had been a perfect sphere (the measurement was made where the balloon was thinner). Thus, a mathematical calculation would be smaller than the actual value, and filling the balloon up with water until it is about the same size is a more accurate representation.
5. The ideal gas law technically applies to ideal gases. Give two differences between a real gas and an ideal gas.
Real gases actually have a volume, while ideal gases are assumed to have particles infinitesimally small. Real gases also do not have elastic collisions like ideal gases do.
6. Would the CO2 you collected in this lab be considered ideal? Why or why not?
The CO2 would not be ideal because gases will behave ideally only when the temperature is very high and the pressure is very low (this allows the particles to move without being restricted and are less likely to be affected by intermolecular forces, which can cause collisions to transfer energy).
Advanced Questions
1. Using info from the label, calculate the mass of CO2 that should be collected per tablet.
2. What is the percent yield?
3. CO2 is water soluble. The solubility around room temperature is around 90mL/100mL of water. What effect does this have on your calculated n value?
This means that not all of the CO2 went in to the balloon as some was dissolved in water. Thus the n value was smaller than expected.
Balloon with CO2 inside.
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