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Chapter 10 – Gas Laws

Chapter 10 – Gas Laws. Kinetic Molecular Theory (KMT). Particles of matter are always in motion. The KMT describes any property based on the particle motion Review: Solids = Rotational Liquids = Rotational & Vibrational Gases = Rotational, Vibrational & Translational. KMT.

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Chapter 10 – Gas Laws

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  1. Chapter 10 – Gas Laws

  2. Kinetic Molecular Theory (KMT) Particles of matter are always in motion. The KMT describes any property based on the particle motion Review: Solids = Rotational Liquids = Rotational & Vibrational Gases = Rotational, Vibrational & Translational

  3. KMT Ideal Gas = A gas that acts “perfectly” as expected. Does not really exist, but it is possible to be close to it.

  4. KMT - Assumptions • Gases are made of large numbers of tiny particles • Particles of a gas are in random, constant straight line motion • Collisions of particles are elastic • There are no attractive or repulsive forces between particles • As temperature increases, speed and energy of the particles increases

  5. KMT http://mc2.cchem.berkeley.edu/Java/molecules/

  6. KMT KE = ½ mv2 **Large molecules move slowly; Small molecules move quickly

  7. Properties of Gases • Most IDEAL when LOW Pressure and HIGH Temperature Why??? • Expansion – Fill entire container • Fluidity – Flow due to minimal external bonds • Low Density – d = m/v

  8. Properties of Gases • Compressibility – Can push particles together to make smaller total volume • Diffusion – Mix / Spread out without stirring Rate1/Rate2 = √Molar Mass2/√M Mass1 Example: How much faster is Hydrogen compared to Oxygen Gas?

  9. Real vs. Ideal Gases Real Gas = Gas that disobeys an assumption of the KMT of Gases • The particles of a real gas have volume themselves. This is ignored by the KMT. • Particles of a real gas have attractive and repulsive forces. These are ignored by the KMT.

  10. Qualitative Description of Gases • Volume of the gas sample • Pressure – Caused by gas particles hitting the sides of the container • Temperature of the gas sample • Number of moles (particles) of the gas

  11. Qualitative Description of Gases • Volume vs. Pressure 2. Temperature vs. Volume 3. Temperature vs. Pressure

  12. Qualitative Description of Gases 4. Moles vs. Pressure 5. Moles vs. Volume

  13. Pressure and Temperature Units mmHg torr (1 torr = 1 mmHg) atm (1 atm = 760 mmHg) kPa (1 atm = 101.325 kPa) Pressure conversion chart will be given to Academic Classes only Standard Temperature = 0oC Standard Pressure = 1 atm STP =

  14. Pressure and Temperature Units K = oC + 273.15 oC = K – 273.15 Temperature Conversion Equations will be given to Academic Classes only

  15. Pressure and Temperature Units Practice Problems:

  16. Measuring Pressure Barometer=A tube filled with Mercury in a “puddle” of mercury.

  17. Measuring Pressure Barometer

  18. Measuring Pressure Manometers = Measures Pressure of a Gas Sample Closed Manometer: Closed End – A vacuum Gas U-Tube with Hg Pgas = Hg Level Difference

  19. Measuring Pressure Open Manometers: Equal Levels: Higher on Atm Side: Higher on Gas Side: Pgas = Patm Pgas = Patm + Hg Diff Pgas = Patm – Hg Diff Skip P=F/A

  20. 10.3 – Quantitative Description of Gases Gas Laws = Numerical descriptions of gas behaviors 1. Boyle’s Law – Volume and Pressure P1V1 = P2V2 (will be given to Academic) Examples:

  21. 10.3 – Quantitative Description of Gases 2. Charles’ Law – Temperature and Volume *Temps must be in Kelvin!! (will be given to Academic) Examples:

  22. 10.3 – Quantitative Description of Gases 3. Gay-Lussac’s Law – Pressure and Temperature *Temps must be in Kelvin!! (will be given to Academic) Examples:

  23. 10.3 – Quantitative Description of Gases 4. Combined Gas Law – A combination of Boyle’s, Charles’, Gay-Lussac’s *Temps must be in Kelvin!! This is really the only one you need to know! (will be given to Academic) If Temperature is CONSTANT = = P1V1 = P2V2 If Pressure is CONSTANT = =

  24. 10.3 – Quantitative Description of Gases 4. Combined Gas Law – A combination of Boyle’s, Charles’, Gay-Lussac’s *Temps must be in Kelvin!! (will be given to Academic) Examples:

  25. 10.3 – Quantitative Description of Gases More Practice:

  26. Dalton’s Law of Partial Pressures Ptotal = P1 + P2 + P3 + … (will be given to Academic) Examples:

  27. Water Displacement (a form of Dalton’s Law)Collecting Gas THROUGH Water The gas collected contains not only the experimental gas, it also contains WATER VAPOR from the water evaporating! The container is moved either up or down to make the gas levels EQUAL. This makes the PRESSURE INSIDE = PRESSURE OUTSIDE! Pgas + PH2O = Ptotal = Patm

  28. Demos • Balloon + Flask • Galileo’s Thermometer • Handboiler • Drinking Bird • Vacuum Pump Tricks • Egg + Flask • Soda Can Crushing

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