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The Gaseous State

The Gaseous State. Gases consist of widely separated molecules in rapid motion. All gases near room temperatures and normal pressures show the same quantitative relationships among their physical properties of pressure , temperature , volume and molar amount.

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The Gaseous State

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  1. The Gaseous State

  2. Gases consist of widely separated molecules in rapid motion. All gases near room temperatures and normal pressures show the same quantitative relationships among their physical properties of pressure,temperature,volume and molar amount.

  3. SI unit of pressure: pascal (Pa) Standard atmosphere: 1 atm = 101325 Pa = 101.325 kPa Temperature: absolute temperature scale, Kelvin scale K = °C + 273.15 T = t + 273

  4. Boyle’s law: The volume of a sample of gas at a given temperature is found to vary inversely with the applied pressure (at fixed temperature for a given amount of gas) PV = constant

  5. Pressure – Volume Data for 1.00g O2 at 0°C

  6. A plot of the volume of 1.000g O2 at 0°C for various pressures.

  7. Charles’ Law Relationship between the volume and the temperature of a gas (Jacques Charles, Joseph Gay-Lussac) Variation of the volume of a sample of gas with temperature (p=const.)

  8. The volume of any sample of a gas varies directly with absolute temperature if the pressure is held constant. The V is not directly proportional to the °C.

  9. Vi= initial volume Vf = final volume Ti= initial temperature Tf= final temperature

  10. -273.15 Temperature-volume curve for an ideal gas (Charles’ law)

  11. Gay-Lussac’s Law At constant volume, the pressure of a given mass of gas varies directly with the absolute temperature. Combined Gas Law

  12. Avogadro’s Law (see stoichiometry) V = nVm n = number of moles Vm = molar gas volume (volume of 6.022 x 1023 gas molecules at a given temperature and pressure)

  13. Standard temperature and pressure (STP) Temperature : 0°C = 273 K Pressure: 1 atm = 101.325 kPa Molar gas volume at STP: 22.41 L/mol

  14. at fixed T, n Boyle’s Law at fixed P, n Charles’ Law a fixed T, P Avogadro’s Law The Ideal Gas Law: Therefore, PV = nRT molar gas constant

  15. J The Ideal Gas Law: Ideal gas: A hypothetical gas that follows the behavior described by the equation of state for an ideal gas.

  16. Gas Mixtures: Dalton’s law of partial pressures: the total pressure of a mixture of gases that do not react is equal to the sum of the partial pressures of all the gases present. Ptotal = pA + pB + pC + …

  17. Kinetic Theory of an Ideal Gas Postulates: • Gases are composed of molecules whose size is negligible compared to the distance between them. • Molecules move randomly in linear motion. • The collosions are elastic. • The average kinetic energy of a molecule is proportional to the K.

  18. Graham’s law of effusion: The rate of effusion of gas molecules from a particular hole is inversely proportional to the square root of the molecular weight of the gas at constant temperature and pressure.

  19. Real gases Van der Waals equation: „a” and „b” are constants

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