Gas Law Lab
Summary
In this lab, students were given a two tablets of Alka Seltzer and were told to collect the CO2 gas it gave off. The crushed Alka Seltzer powder mixed with water would cause the balloon to inflate, then measuring the circumference of the balloon using a string. Then, using the ideal gas law and finding the volume of the sphere, students could determine the mass of the gas.
Data Table and Calculations
Analysis Questions
1) When we were transferring the water from the balloon to the graduated cylinder, some water splashed out. Also, while we where measuring the circumference of the balloon with the string, it wasn't perfectly in the middle.
2) The error from the above question of losing water while transfering it would cause the number of moles of CO2 to be too large. This is because the volume of the water that fits in the balloon would be greater, and therefore when you solve for the amount of moles of CO2 in the ideal gas law, it would turn out larger.
3)
C=2πr
35.0 =2πr
r=5.57 cm
V=(4/3)πr^3
V=(4/3)π(5.57)^3
V=724 mL
4) My answer to #3 and the volume obtained by filling the balloon with water is fairly close, with a difference of 38 mL. I felt that our volume obtained by filling up the balloon was more accurate than our calculated value because our balloon was not a perfect sphere, and the calculated value used a formula for finding the volume of a perfect sphere.
5) A difference between a real gas and an ideal gas is that real gases obey gas laws only at low pressures and high temperature, while ideal gases obey all gas laws under every condition of temperature and pressure. Another difference between a real gas and an ideal gas is that a real gas obeys the Van Der Waals equation while an ideal gas obeys the ideal gas law.
Advanced Questions
3) Our calculated "n" value will be more accurate because the calculated volume of CO2 will be less. Some of the carbon dioxide would have dissolved into the water, and not be transfered into the balloon.
Balloon Image
In this lab, students were given a two tablets of Alka Seltzer and were told to collect the CO2 gas it gave off. The crushed Alka Seltzer powder mixed with water would cause the balloon to inflate, then measuring the circumference of the balloon using a string. Then, using the ideal gas law and finding the volume of the sphere, students could determine the mass of the gas.
Data Table and Calculations
Analysis Questions
1) When we were transferring the water from the balloon to the graduated cylinder, some water splashed out. Also, while we where measuring the circumference of the balloon with the string, it wasn't perfectly in the middle.
2) The error from the above question of losing water while transfering it would cause the number of moles of CO2 to be too large. This is because the volume of the water that fits in the balloon would be greater, and therefore when you solve for the amount of moles of CO2 in the ideal gas law, it would turn out larger.
3)
C=2πr
35.0 =2πr
r=5.57 cm
V=(4/3)πr^3
V=(4/3)π(5.57)^3
V=724 mL
4) My answer to #3 and the volume obtained by filling the balloon with water is fairly close, with a difference of 38 mL. I felt that our volume obtained by filling up the balloon was more accurate than our calculated value because our balloon was not a perfect sphere, and the calculated value used a formula for finding the volume of a perfect sphere.
5) A difference between a real gas and an ideal gas is that real gases obey gas laws only at low pressures and high temperature, while ideal gases obey all gas laws under every condition of temperature and pressure. Another difference between a real gas and an ideal gas is that a real gas obeys the Van Der Waals equation while an ideal gas obeys the ideal gas law.
Advanced Questions
3) Our calculated "n" value will be more accurate because the calculated volume of CO2 will be less. Some of the carbon dioxide would have dissolved into the water, and not be transfered into the balloon.
Balloon Image
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| Balloon inflated with the CO2 gas |
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