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Catalyst

Catalyst. 1. The volume of hydrogen collected over water is 453 mL at 18 o C and 780 mm Hg. What is the pressure of hydrogen. NOTE – the vapor pressure of water at 18 o C is 15.5 mm Hg. What Does Energy Look Like?. Lecture 4.3 – Kinetic Molecular Theory. Today’s Learning Targets.

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Catalyst

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  1. Catalyst 1. The volume of hydrogen collected over water is 453 mL at 18 oC and 780 mm Hg. What is the pressure of hydrogen. NOTE – the vapor pressure of water at 18 oC is 15.5 mm Hg.

  2. What Does Energy Look Like?

  3. Lecture 4.3 – Kinetic Molecular Theory

  4. Today’s Learning Targets • LT 4.5 – I can explain the five postulates of the Kinetic Molecular Theory and discuss how the motion of molecules relates to temperature. Furthermore, I can interpret a gas energy graph and relate it to this theory.

  5. Kinetic Energy • Kinetic Energy is the energy of moving molecules • Any object that has mass and moves has a kinetic energy associated with it.

  6. Why Do These Properties Exist? • The ideal gas law states that: PV = nRT • While this equation tells us very specific values, it does not tell us why these properties exist. • The Kinetic Molecular Theory provides a why for the observed properties for temperature and pressure.

  7. Postulates of Kinetic Molecular Theory 1. Gases consist of large numbers of molecule that are in continuous, random motion.

  8. Postulates of Kinetic Molecular Theory 2. The size of gas molecules are negligible in comparison to the overall volume where the gas is contained

  9. Postulates of Kinetic Molecular Theory 3. Attractive and repulsive forces between gas molecules are negligible

  10. Postulates of Kinetic Molecular Theory 4. Molecules inside a container collide, but the collisions result in no loss of energy and kinetic energy is conserved.

  11. Postulates of Kinetic Molecular Theory 5. The average kinetic energy of the molecules is proportional to the temperature. Temperature provides a reading of the average kinetic energy of a sample of gas.

  12. Application of KMT to Ideal Gas Law • When we look at gas laws, we can explain the observed properties using KMT • Any observed gas law can be explained through this lens

  13. E.g. Pressure Explained by KMT • Molecules collide with each other and the wall of the container. • These collisions are what leads to observable pressures.

  14. Temperature and Kinetic Energy • The temperature represents the average kinetic energy. • Therefore, if you double the temperature, then you double the average kinetic energy • Remember, this is only the average

  15. Kinetic Energy of Gases • KMT states states that the kinetic energy of any gas is: KE = ½mu2 • Where m = mass of the gas and u = root mean square speed of the gas. • The value of u can be calculated by:

  16. Distribution of Molecular Speed • The temperature tells us the average speed/kinetic energy of the molecules, but the molecules have a wide range of speeds The average speed at 0 oC is lower than at 100 oC, therefore KE is lower

  17. Heavier gases have lower u values, so a greater fraction of their molecules can be found moving at slower speeds

  18. Error Analysis • There are 8 questions posted throughout the room. • Each question has some error. • Analyze the problem, determine the error, and check your answer by pulling paper back.

  19. Closing Time • Read 10.7 • Complete write – up for butane lab (Due next Monday/Tuesday) • Pre – lab for Carbonate lab due Thursday/Friday • Meeting Make-Ups • Class Picture

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