Gay-Lussac's Law

Klara Beinhorn P6

Background

Joseph Gay- Lussac was a French chemist and physicist who came up with what is most commonly known as Lussac's Law in 1808. This law states that, "A law stating that the volumes of gases undergoing a reaction at constant pressure and temperature are in a simple ratio to each other and to that of the product." This basically means that volume and pressure are directly related; as one increases, the other increases as well and vice versa. As gases are heated up, their kinetic energy increases; consequestly, the gas molcules take up more space thus increasing the pressure. This lab will explore this relationship and physically prove the law by using different temperatures of water in order to change pressure while the amount of gas and volume remain constant by using an Erlenmyer flask. Pressure will then be measured with a Gas Pressure Sensor while temperature will be monitored with a Temperature Probe all ran through the Logger Pro computer program.

Procedure

  1. Obtain the already prepared ice water, room temperature, and hot water buckets. (when your group is done, pass them on to the next group)
  2. Connect the Temperature Probe and the Gas Pressure Sensor into CH1 and CH2 of the computer interface. Then connect the computer interface to your computer through the USB port.
  3. Open Logger Pro and open the file "07 Pressure- Temperature" from the Chemistry with Computers folders of Logger Pro. .
  4. Insert the robber stopper along with the heavy-wall plastic tubing to the open stem of the Gas Pressure Sensor.
  5. Insert the rubber-stopper assembly into a 125 mL Erlenmeyer flask.
  6. Close the the two-way valve by turning the valve so it is perpendicular with the valve stem.
  7. Click collect to begin collection -collect pressure vs. temperature data for your gas sample.
  8. Now place the flask in the bucket with cold water along with the temperature probe until the readings on logger pro stop moving.
  9. Repeat step 8 for the other buckets. (be sure to go from cold to hot)
  10. Click stop when you have finished collecting the data. Record the pressure and temperature values in the data table provided.
  11. Examine the graph in order to decide if it is direct or inversely related.
  12. Change the temperature scale to Kelvins in order to make it an absolute value temperature scale.- choose new calculated column from the data menu, enter "Temp Kelvin" as name, "T Kelvin" as short name, and "K" as unit. Enter the formula 273+.
  13. Click Curve Fit, try a fit, and auto scale the graph. Use the snipping tool to copy the graph onto your lab.

Observations

  • When the flask entered the cold water, pressure decreased.
  • When the flask entered the hot water, pressure increased.
  • Observed the graph making a linear line
  • As temperature increased, volume increased and vice versa = directly related.

Graph

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Molecular Model

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Conclusion

We discovered that Lussac's Law creates a direct relationship meaning: as temperature increases, pressure increases. The graph produces a linear fit because of this direct relationship. This happens because as temperature increases, so does the kinetic energy of the gas molecules which will consequently take up more space. If no more space is there, then the pressure will increase to compensate for this movement. We can solve equations by setting up a proportion because they are directly related.

Bibliography

"Definition of Gay-Lussac's Law in English:." Gay-Lussac's Law: Definition of Gay-Lussac's Law in Oxford Dictionary (American English) (US). N.p., n.d. Web. 29 Apr. 2016.

"Joseph Louis Gay-Lussac." Wikipedia. Wikimedia Foundation, n.d. Web. 29 Apr. 2016.