Charles Law Lab

Honors Chemistry Name

Chapter 13: Charles’ Law Lab Date _____/_____/_____ Period _____

Purpose: The purpose of this experiment is to clarify the relationships between volume, temperature, and pressure and to test the validity of Charles’ Law by completing calculations with the collected data. A quantity of air at about 100 oC will be cooled to a temperature of about 0 oC. The experimentally determined volume change will be compared with V2 and predicted mathematically by Charles’ Law.

Procedure: 1. Arrange the apparatus as demonstrated in class. Draw a diagram below of how you are to hold the Erlenmeyer flask during the temperature change. This diagram will need to be in your laboratory write-up.

Use a wax pencil to mark the position of the bottom of the rubber stopper for later use in the experiment. Immerse the dry flask assembly up to the neck of the Erlenmeyer flask in the water and heat to boiling. Allow the flask to stand in the boiling water for approximately 8 minutes. Record the temperature of the boiling water, T1.

2. Press your finger firmly over the glass tube and remove the flask from the boiling water. This can be done without getting burned if you hold on to the rubber stopper. Invert the Erlenmeyer flask into the sink that is filled with below room temperature water. Make sure that the flask is completely submerged. After about 1 minute, release your finger and observe what happens. Be sure to keep holding the flask under the surface.

3. Record the temperature of the cold water bath, T2. When no further changes are observed raise the flask so that the water level inside the flask coincides with the water level outside, while keeping the glass tube under the water. Remove the flask by again covering the glass tube with your finger. Stand the flask upright on your bench. Dry the outside of the flask and measure the volume of water inside the flask by pouring the water into a 100 mL graduated cylinder. Record the volume as Vw. After completing this measurement, fill the used flask with water to the wax pencil line and measure the water by pouring it into the 250 mL graduated cylinder. If all of the water does not fit, record and repeat. This recorded volume is V1. Data: (Trial 1) (Trial 2) (Trial 3)

1. T1 of the gas (Hot water Bath) = ______K ______K ______K

2. T2 of the gas (Cold Water Bath) = ______K ______K ______K

3. Vw (Volume of the water that = ______mL ______mL ______mL entered the flask)

4. V1 (Total Volume of the Flask) = ______mL ______mL ______mL

5. V2 = (V1 – Vw) = ______mL ______mL ______mL

Calculations:

1. Using Charles’ Law, calculate the theoretical second volume, V2 theoretical.

2. Calculate the percent error.

Questions: (Complete the following questions on a separate piece of paper.)

1. As the air inside the flask is heated, what is happening to its volume?

2. What happened after your finger was released? Why did this occur?

3. What is the relationship between the volume of water entering the flask and the decrease in volume of the air inside the flask as it cooled.

4. What was the reason for making the water levels coincide before putting your finger over the tube and removing the flask from the water?

5. What is the gas used in this experiment?

6. State Charles’ Law in words.

7. Since the cooled gas was collected “over water”, Dalton’s Law of Partial Pressure must be applied. A pressure correction is determined by subtracting the water vapor pressure from the atmospheric pressure to get P2 while atmospheric pressure is used as P1. Using this information, calculate the theoretical V2 for the experiment using the ideal gas law for two gases.

8. Is the theoretical V2 calculated using the ideal gas law any closer to the experimental V2 than the V2 calculated using Charles’ Law? Explain why or why not.

9. Calculate the percent error for theoretic V2 calculated using the ideal gas law..