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Diffusion, STP, and Ideal Gas Law

Diffusion, STP, and Ideal Gas Law. 12-10-09. Diffusion. Diffusion – movement of particles from a region of higher density to a region of lower density; this is caused by the random motion of molecules. What happens if I release open a container filled with green gas?.

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Diffusion, STP, and Ideal Gas Law

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  1. Diffusion, STP, and Ideal Gas Law 12-10-09

  2. Diffusion • Diffusion – movement of particles from a region of higher density to a region of lower density; this is caused by the random motion of molecules What happens if I release open a container filled with green gas?

  3. Dalton’s law of partial pressures • Dalton’s Law of Partial Pressure – the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases Ptotal = PA + PB + PC … B A C A In this cylinder, which type of gas molecule will have the highest partial pressure? A A B B B C A A B C Molecule A

  4. Practice Partial pressures • If the partial pressure of A is 6 atm (PA = 6), the partial pressure of B is 5 atm (PB = 5), and the partial pressure of C is 3 atm (PC = 3), what is the total pressure of the container?

  5. Derive ideal gas law • Variables • Pressure • Temperature • Volume • Number of Molecules (Moles) What happens to the pressure when we change these? Increase Temperature = Increase Pressure Increase Volume= Decrease Pressure Increase Moles = Increase Pressure

  6. Ideal gas law • Ideal Gas – gas in which molecules keep the exact same speed after collisions. In other words, friction does not slow them down • Can approximate most gases as ideal • PV = nRT • P = Pressure • V = Volume • n = number of moles • R = Ideal Gas Constant • T = temperature

  7. Ideal gas constant • R = Ideal Gas Constant • R = 8.314 • R = 0.0821

  8. Review: celsius and kelvin • Celsius to Kelvin • TK = TC + 273 • Kelvin to Celsius • Tc = TK - 273 The temperature in Kelvin is always bigger than the temperature in Celsius!! TK > TC

  9. Standard temperature and pressure • Because gases are easily affected by temperature and pressure changes, we need a standard pressure and temperature to refer to • Standard Temperature and Pressure (STP) • Temperature = 0 degrees C • Pressure = 1 atm

  10. Standard Temperature and Pressure & Ideal gas law • Let’s use PV=nRT to find the volume of 1.00 mol of an ideal gas at STP. • P = 1 atm • V = ? • n = 1.00 mol • R = 0.0821 • T = 0 degrees celsius + 273 Kelvin = 273 Kelvin

  11. More ideal gas Problems • What pressure has a container with 1.20 moles of gas, 14.88 L, and 25 degrees Celsius?

  12. More Ideal Gas Problems • A balloon has a volume of 15.9 L, 149 kPa, and a temperature of 28 degrees C. How many moles of gas are in the balloon?

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