Practical examples of the gas laws  (Page 2/2)

Note: The formula of carvone is $C_{\text{10}}{H}_{\text{14}}O$ , MW=150.22 g/mol.

Since, PV = nRT

and nRT = (1/3)Nm ${\mu }^2$ .

Solving for $\mu$ gives:

$\mu$ = $\sqrt{3\text{RT}/M}$ .

where M = mN/n or the molar mass in kg/mol, T is in k, and R is 8.3145 $\text{kg}\ast m^2/s^2\ast \text{mol}\ast K$ . The $\mu$ , we are using is the root mean square speed, as it is the root of the sum of the squares of the individual velocities.

The plots can be prepared when you have finished the lab.

• Gas Laws in a Soda Can:

• Pour 15 mL of water into an aluminum soda can. Set the can on a hot plate and turn on to a high temperature setting. While the can water heats, fill a 1000-mL beaker with cold water (You may have a metal tin set out for this purpose). Continue heating the can until the water inside boils vigorously and until steam escapes from the mouth of the can for about 20 seconds.
• Using the hot grips to grip the can near the bottom, quickly lift the can from the burner and invert it in the beaker of cold water so water covers the mouth of the can.
• Describe what happens.
• Explain why it happens. You may repeat this experiment using a second soda can if you wish.
• Why is it necessary to invert the can in the water? What would happen if a rigid container were used?
•  Balloon in liquid nitrogen:

Review the safety notes above regarding the handling of liquid nitrogen.

1. Inflate a balloon and tie the end (several balloons may have already been inflated and tied). Using tongs, place the balloon in a Dewar flask containing liquid nitrogen. After the balloon stops changing size, remove it from the Dewar and allow it to warm to room temperature.

2. Observe and record the changes (you should be able to measure the radius and estimate volume). Estimate the size of the balloon in liters.

3. What is the pressure inside the balloon before it is placed in the liquid nitrogen?

4. What is the pressure inside the balloon after it is placed in the liquid nitrogen?

5. Use the ideal gas law to calculate the percent change in volume expected on going from room temperature to liquid nitrogen temperature.

6. Is the volume of the cold balloon consistent with what you calculated, or is it larger or smaller?

7. Suggest an explanation for your observation. Explain all of your observations in detail using the kinetic molecular theory of gases.

8. How does the liquid nitrogen cool the gas in the balloon?

•  Kissell's tygon tube in liquid nitrogen:

Review the safety notes above regarding the handling of liquid nitrogen. 

• Place a 2 foot long tygon clear tube in a Dewar with liquid nitrogen.
• Observe what happens and explain.
• Balloon in a flask:

• Place about 5 mL of water in a 125-mL Erlenmeyer flask. Heat the flask on a hot plate until the water boils down to a volume of about 1 mL.
• Meanwhile, inflate a balloon and then let the air out (this may not be necessary if balloons on table have been previously used).
• Remove the flask from the heat, hold it with a towel, and immediately place the open end of the balloon over the mouth of the flask.
• Observe the effect as the flask cools.
• Can you get the balloon back out again?
• If you can, How?
•  Cartesian diver:

The Cartesian diver is named for Rene Descartes (1596-1650), noted French scientist and philosopher. At this station, you will find a plastic soda bottle containing a medicine dropper, water, and air. Squeeze the bottle. 

What happens? Why?

• The Egg:

• Lightly grease the inside of the neck of a 1 L Erlenmeyer flask with stopcock grease. Clamp the flask onto the stand. Place about 5 mL $H_{2}O$ in the flask and gently warm it with a Bunsen burner until the water vaporizes. Do not boil the water to dryness.
• Meanwhile, prepare an ice water bath in an evaporating dish. While the flask is warm, seat the egg, narrow end down, in the mouth of the flask. Unclamp the flask, allow to cool slightly sitting on the bench and then immerse it in the ice water. (Read the safety notes above to avoid breaking the flask)
• Can you get the egg back out again?
• Assuming that the flask reaches the maximum vacuum (minimum pressure) possible before the egg is drawn into the flask, calculate the minimum pressure reached in the flask.
• Expanding balloon:

• Partially inflate a balloon. Place the balloon inside the vacuum chamber and close the chamber with the black rubber circle and the top of the chamber carefully centered on the base (A partially inflated balloon may already be in the dessicator).
• Close the needle valve (at the bottom of the black rubber tubing) by turning it clockwise. Turn the stopcock to the up position to connect the chamber to the vacuum pump.
• What happens? Explain? To open the chamber, turn the stopcock to the left position and open the needle valve.

Moore's bonus 2 points: 

1pt to name a real life example of the physical properties of gases at work

1pt for a good explanation of how and why it works according to what you have learned in the lab.