1 / 28

Combined Gas Law

Combined Gas Law. Agenda Demos & Notes on gas laws Homework: Gas Laws. Combined Gas Law. Date:. Kinetic Molecular Theory. The theory that a gas consists of molecules in constant random motion. Postulate 1.

megan-douglas
Download Presentation

Combined Gas Law

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Combined Gas Law Agenda • Demos & Notes on gas laws • Homework: Gas Laws

  2. Combined Gas Law Date:

  3. Kinetic Molecular Theory The theory that a gas consists of molecules in constant random motion.

  4. Postulate 1 • Gases are composed of molecules whose size is negligible compared with the average distance between them.

  5. Postulate 2 • Molecules move randomly in straight lines in all directions and at various speeds. • Pressure is the same in all directions • Changes directions when it collides

  6. Postulate 3 • The forces of attraction or repulsion between two molecules in a gas are very weak or negligible, except when they collide.

  7. Postulate 4 • When molecules collide with one another, the collisions are elastic.

  8. Postulate 5 • The average kinetic energy of a molecule is proportional to the absolute temperature.

  9. Variables • P: pressure • V: volume • T: temperature – must be in Kelvin • Celsius, oC and Kelvin • oC + 273 = K

  10. Pressure • Force exerted per unit of area • Has multiple units: psi, kg/ms2 = pascal, mmHg = torr, atm. • Evagelista Torricelli created the mercury barometer

  11. Standard Pressure • 1 atm = 760 torr = 760 mmHg = 101.3 kPa • Convert between units using std pressures as conversion factors.

  12. Temperature • Measure of the average kinetic energy of the molecules.

  13. Volume • The space occupied by matter • For which state of matter can the volume be changed simply by changing the pressure or temperature?

  14. What does a vacuum pump do? Decreases the pressure by removing air molecules

  15. Observe the balloon and marshmallow. What is the relationship between pressure and volume?

  16. Modified Volcano • Vinegar and baking soda make CO2. • As more MC of gas are created, pressure increases and it needs more volume. • Stopper blows

  17. Boyles Law • P1V1 = P2V2 • Pressure varies inversely with volume.

  18. This little light of mine • Flame burning = high T, MC moving fast = high P and take up more space. • Cover with graduated cylinder, use up all O2 flame goes out instantly reducing T. • Less movement, less pressure. • Atm forces liquid up!

  19. Gay – Lussac Law • P1T2 = P2T1 • Pressure varies directly with temperature. • Temperature MUST be in Kelvin and is not used to determine SF.

  20. Hand Warmer • Cold jar, balloon deflated • Warm jar, increase T, volume of balloon increases.

  21. Charles Law • V1T2 = V2T1 • Volume varies directly with temperature. • Temperature MUST be in Kelvin and is not used to determine SF.

  22. Fountain • Increase pressure in container, by decreasing space between gas molecules. • Stop blowing, releases pressure and creates more space by spraying water!

  23. Combined Gas Law • P1V1T2 = P2V2T1 • Shows the relations between variables and predicts results of adjustments made to system. • Use for changing conditions! • If one variable is constant, enter the same value twice or remove that variable from the equation.

  24. STP Conditions • Standard temperature is 273 K • Standard pressure can be • 1 atm • 101.3 kPa • 760 torr • 760 mmHg

  25. V1 P1 A 50. L sample of a gas at a pressure of 1.0 atm and a temperature of 25oC is moved to an area where the pressure is 5.0 atm and the temperature is 30oC. What is the new volume of the gas? T1 P2 T2 • P1V1T2 = P2V2T1 • (1.0atm)(50.L)(30+273K) = (5.0atm)(X)(25+273) • 15150 = 1490X • 10. L

  26. V1 P1 A 50.0 mL sample of a gas has a pressure of 2.00 atm when the temperature is 25oC. What volume will the gas occupy at a pressure of 4.00 atm when a constant T? T1 P2 • P1V1T2 = P2V2T1 • (2.00atm)(50.0mL) = (4.00atm)(X) • 100 = 4X • 25.0 L

  27. V1 T1 P1 A 5.0 mL sample at 20oC has a pressure of 1.0 atm. What volume will the gas occupy when the temperature is raised to 60oC at constant pressure? T2 • P1V1T2 = P2V2T1 • (5.0mL)(60+273) = (X)(20+273) • 1665 = 293X • 5.7 mL

  28. P1 V1 A 20.0 mL sample of a gas has a pressure of 2.0 atm at a temperature of 20oC. What will the temperature be when the pressure is raised to 4.0 atm at a constant volume. T1 P2 • P1V1T2 = P2V2T1 • (2.0atm)(X) = (4.0atm)(20+273) • 2X = 1172 • 586K

More Related