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12.3 Presentation Transcript

  • 1. Putting it all together… Chapter 12 section 3 Slides 1-5 = Ideal Gas Law
  • 2. Ideal Gas Law Relates 4 Gas Variables
    • PV = nRT
    • The value for R depends on the units used for pressure and volume.
    • Volume must be in liters
  • 3. R
    • For problems that use units of kilopascals and liters when using the ideal gas law, the value you will use for R is as follows.
    • If the pressure is expressed in atmospheres , then the value of R is 0.08206 (L•atm)/(mol•K) .
  • 4. Ideal Gas Law Sample Problem How many moles of gas are contained in 22.41 liters at 101.325 kPa and 0°C?
  • 5. 1.00 mol Ideal Gas Law Sample Problem Solution V = 22.41 L T = 0°C P = 101.325 kPa n = ? 0°C + 273 = 273 K PV = nRT
  • 6. Diffusion
    • Gaseous molecules travel at high speeds in all directions and mix quickly with molecules of gases in the air in a process called diffusion.
    • Diffusion is the movement of particles from regions of higher density to regions of lower density.
    • During diffusion, a substance moves from a region of high concentration to a region of lower concentration .
    • Eventually, the mixture becomes homogeneous.
    • Large molecules diffuse slower than small molecules.
  • 7. Dalton’s Law of Partial Pressure
    • In 1805, John Dalton showed that in a mixture of gases, each gas exerts a certain pressure as if it were alone with no other gases mixed with it.
    • The pressure of each gas in a mixture is called the partial pressure.
    • The total pressure of a mixture of gases is the sum of the partial pressures of the gases. This principle is known as Dalton’s law of partial pressure.
  • 8. Dalton’s Law of Partial Pressure
    • Dalton’s law of partial pressure can be written as follows.
    • P total = P A + P B + P C
      • P total is the total pressure, and P A , P B , and P C are the partial pressures of each gas.
  • 9. Gas Volumes Correspond to Mole Ratios
    • Ratios of gas volumes will be the same as mole ratios of gases in balanced equations.
    • Avogadro’s law shows that the mole ratio of two gases at the same temperature and pressure is the same as the volume ratio of the two gases.
  • 10. Gas Volumes Correspond to Mole Ratios
    • For example, consider the following equation for the production of ammonia.
    • 3 H 2 ( g ) + N 2 ( g ) -> 2 NH 3 ( g )
    • 3 L of H 2 react with 1 L of N 2 to form 2 L of NH 3 , and no H 2 or N 2 is left over
    • If we know the number of moles of a gaseous substance, we can use the ideal gas law to calculate the volume of that gas.