Name: ______Date: ______Period: ____
Name: ______
Name: ______
LAB – Gas Laws & the Ideal Gas Law
(Balloons, Marshmallows, and Air)
Introduction:
Gas laws relate temperature, pressure, volume and amount of gases. In this lab, you will use marshmallows and plastic syringes to test one of the basic gas laws. You will use a balloon and a flask to test another basic gas law. You will use air and a scale to calculate the molar mass of air with the ideal gas law. You will then write a conclusion relating the observations, data, and calculationsto each gas law you tested.
Purpose:
Test two basic gas laws and develop a conclusion about how temperature, volume, and pressure are related. Calculate the molar mass of air from measurements and the ideal gas law.
Materials:
large syringeballoon (small)hot plate
marshmallows (2)125-mL flask nail
Part I:Boyle’s Law (Pressure and Volume)
1.Pull the plunger complete out of the syringe. Replace it and remove it again. Record your observations in the data table.
2.Place a marshmallow in the syringe. Hold your finger over the end and compress the plunger as far as you can. Pull the plunger back and compress it again. Record your observations of the marshmallow in the data table.
3.Remove the marshmallow and place new one in the syringe. With your finger OFF the end (leave the end open) compress the plunger down to the marshmallow but do not touch it.
Hold your finger over the end and pull the plunger up to the maximum volume but not out of the syringe. Release the plunger and pull it up again. Record your observations of the marshmallow in the data table.
Part II:Charles’ Law (Volume and Temperature)
4.Place about 20 mL of water into a 125-mL flask. Place it on the hot plate and set the plate on high.
Allow the water to reach a full boil, and allow it to boil for 1 minute filling the flask with hot water vapor (gas).
5.Be VERY CAREFUL with this step (ask me for help if needed).
Hold the mouth of a balloon wide open with your fingers and carefully slip it over the top of the flask. Then remove the flask from the hot plate and turn it off. Record your observations of the balloon in the data table.
Part III:Molar Mass of Air(w/ Ideal Gas Law)
6.Completely compress the syringe to 0 mL and turn the end cap until it is locked and sealed.
While one student firmly holds the syringe barrel, another student will pull out the plunger far enough to expose the hole through it. Another student will place the nail through the hole and the plunger may then be released.
7.Place the evacuated syringe (with nail) on the scale and record the mass. Record the exact volume to which the plunger is pulled.
8.Remove the nail, followed by removing the end cap so the syringe end is now open. Pull the plunger out to exactly the same volume as in Step 6 and seal it with the end cap again.
Place the air-filled syringe AND nail on the scale and record the mass.
9.Ask your instructor for the temperature and pressure of the lab room and record these values in your data table. Calculate the mass of air in the syringe and record it in the data table
10.Remove the balloon from the flask. Throw away the marshmallows. Return the flask, balloon, nail, and syringe (with end cap).
Data & Observations: (20 pts.)
Boyle’s Law
(Step 1)Observation of plunger removal: ______
Explanation of what you observed: ______
______
(Step 2)When you compressed the plunger, what happened to thepressure? increaseordecrease
What did this change do to the volume of the marshmallow? increaseordecrease
(Step 3)When you pulled the plunger up, what did you do to the pressure? increaseordecrease
What did this change do to the volume of the marshmallow? increaseordecrease
Charles’ Law
(Step 4)When you increased the temperature, what happened to the volumeof the water vapor? increaseordecrease
(Step 5)Observation of balloon on flask: ______
Explanation of what you observed: ______
______
When the water vapor in the flask cooled (temperaturedecreased),
what happened to the volume of the water vapor? increaseordecrease
Molar Mass of Air (using Ideal Gas Law)
Volume: ______mL = ______L
Mass (evacuated syringe): ______gMass (air-filled syringe): ______g
Mass (air): ______g
Pressure: ______mmHg = ______atm
Temperature: ______oC = ______K
Calculations: (10 pts.)
1.Write the Ideal Gas Law and list each variable with a name and unit:
2.Use the ideal gas law to calculate the number of moles of gas in the sample of air.
3.Use the mass of air (data table) and the moles of air (#2 above) to calculate the molar mass of air in g/mol.
4.The theoretical (or true) value for the molar mass of dry air is 28.97 g/mol.
Calculate the % error for your experimental value (#3 above).
Recall:% error = (experimental–theoretical) x 100
theoretical
5.Use the ideal gas law and the true molar mass of air (28.97 g/mol) to calculate the mass of air at STP in an empty refrigerator with a volume of 1200 L. (2 steps)
OVER→
(Conclusion on back)
Conclusion: (30 pts.)
State the relation between Pressure and Volume that you observed in Part I: Boyle’s Law.
______
______
______
Are Pressure and Volume inverselyordirectly proportional?
State the relation between Volume and Temperature that you observed in Part II: Charles’ Law.
______
______
______
Are Volume and Temperature inverselyordirectly proportional?
Discuss your findings about the molar mass of air. Include your thoughts about sources of error, and convince me that you completely understand the principles and calculations involved.
______
______
______
______
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