1 / 29

Gas!!!

Gas!!!. It’s Everywhere!!!!. Kinetic Molecular Theory. Most of the volume occupied by a gas is empty space Collisions between gas particles are elastic collisions Energy is transferred between the particles. Kinetic Molecular Theory. Gas particles are in constant motion

oleg-bowers
Download Presentation

Gas!!!

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. Gas!!! It’s Everywhere!!!!

  2. Kinetic Molecular Theory • Most of the volume occupied by a gas is empty space • Collisions between gas particles are elastic collisions • Energy is transferred between the particles

  3. Kinetic Molecular Theory • Gas particles are in constant motion • Possess kinetic energy (energy of motion) • Kinetic Energy in a gas depends on the temperature • KE = ½ mv2

  4. Kinetic Molecular Theory • Expansion • No definite shape or volume • Fluidity • Gases flow like liquids • Low Density • Most of the volume is empty space • Compressibility • Since mostly empty space, particles can be squeezed into a smaller volume

  5. Diffusion • Spontaneous mixing of gas particles caused by their random motion

  6. Effusion • A process by which gas particles pass through a small opening

  7. Diffusion vs. Effusion

  8. Real vs. Ideal • Ideal Gas – An imaginary gas that perfectly fits all of the assumptions of the Kinetic Molecular Theory • Real Gas – A gas that does not behave completely according to the assumptions of the Kinetic Molecular Theory • A real gas can behave like an ideal gas under high temperature and low pressure conditions

  9. STP • STP = Standard Temperature and Pressure • Standard Temperature = 0°C • Standard Pressure = 1 atm

  10. Pressure • The force per unit area on a surface • Barometer – a device used to measure atmospheric pressure

  11. Units of Pressure • Millimeters of mercury – mmHg • Torr • Atmosphere – atm • Pascal – Pa • Kilopascal - kPa

  12. Important Conversion • 1 atm = 760 mmHg • 1 atm = 760 torr • 1 atm = 101.325 kPa

  13. Temperature • Kelvin is the standard temperature scale used when dealing with gases • Absolute zero = 0 K • Unreachable! • Temperature in Kelvin = Temperature in Celsius + 273 • Temperature in Celsius = Temperature in Kelvin – 273 0°C = 273 K 25°C = 298 K (Room Temp) 0 K = -273°C (Absolute Zero)

  14. Boyle’s Law • The volume of a gas at constant temperature varies indirectly with pressure.

  15. Example • The pressure exerted on a 240 mL sample of hydrogen gas at constant temperature is increased from 0.428 atm to 0.724 atm. What will the final volume of the sample be? • V1 = 240.0 mL • V2= ? • P1 = 0.428 atm • P2 = 0.724 atm P1V1 = P2V2 (0.428 atm)(240.0 mL) = (0.724 atm)V2 V2 = 142 mL

  16. Charles’ Law • The volume of a gas at constant pressure varies directly with the temperature

  17. Example • A sample of air has a volume of 140.0 mL at 67°C. At what temperature will its volume be 50.0 mL at constant pressure? • V1 = 140.0 mL • V2= 50.0 mL • T1 = 67°C + 273 = 340 K • T2 = ? V1 V2 V2 T1 (50.0 mL)(340K) T2 = = = 121 K = 140.0 mL T1 T2 V1

  18. Gay-Lussac’s Law • The pressure of a gas at constant volume varies directly with the temperature

  19. Combined Gas Law

  20. Example • A helium filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10°C?

  21. Solution • V1 = 50.0 L • V2= ???? • P1 = 1.08 atm • P2 = 0.855 atm • T1 = 25°C + 273 = 298 K • T2 = 10°C + 273 = 283 K Step 1: List what you are given. Must Convert to Kelvin!!!!

  22. Solution Step 2: Solve the Combined Gas Law for your unknown.

  23. Solution Step 3: Solve! (1.08 atm)(50.0 L)(283 K) V2 = (0.855 atm)(298 K) V2 = 60.0 L He

  24. Dalton’s Law • The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. PT = P1 + P2 + ..... + Pn

  25. Example • What is the total pressure of a gas containing a mixture of three gases whose partial pressures are 20 kPa, 10 kPa, and 30 kPa? PT = P1 + P2 + ..... + Pn PT = 20 kPa + 10 kPa + 30 kPa PT = 60 kPa

  26. Ideal Gas Law • The mathematical relationship among pressure, volume, temperature, and the number of moles of a gas.

  27. Example • Calculate the volume, in liters, occupied by 2.00 mol of H2 at 300 K and 1.25 atm. (R = 0.0821) PV = nRT nRT V = P (2.00mol)(0.0821)(300K) V = 1.25 atm V = 39.4 L

  28. Avogadro’s Law • Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

  29. Gas Stoichiometry 2CO + O2 2CO2 How many liters of oxygen are required to produce 2 L of carbon dioxide? 2L CO2 1L O2 = 1L O2 2L CO2

More Related