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KINETIC MOLECULAR THEORY

KINETIC MOLECULAR THEORY. Kinetic Molecular Theory. A theory that explains the physical properties of gases by describing the behavior of subatomic particles. Physical Properties of Gases:. Gases have mass Gases are easily compressed Gases completely fill their containers

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KINETIC MOLECULAR THEORY

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  1. KINETICMOLECULARTHEORY

  2. Kinetic Molecular Theory A theory that explains the physical properties of gases by describing the behavior of subatomic particles

  3. Physical Properties of Gases: • Gases have mass • Gases are easily compressed • Gases completely fill their containers • Gases diffuse rapidly • Gases exert pressure

  4. KMT has 5postulates:

  5. #1 A gas consists of very small particles that have mass. (molecules or atoms)

  6. #2 Gas particles are very far apart from each other. (therefore gases are easily compressed)

  7. #3 Gas particles are in continuous, rapid, random motion.

  8. #4 Collisions of gas particles (with each other and with container) are perfectly elastic (no energy lost)

  9. #5 The average energy of the gas particles depends on the temperature of the gas.

  10. We can measure gases in 4 ways:

  11. Temperature (T) A measurement of the average kinetic energy of a substance

  12. Higher temperatures cause gas particles to move faster

  13. K = °C + 273 14°C = ? K 14°C + 273 = 287K To solve gas problems, the temp must always be in Kelvin (K) !!!

  14. Pressure (P) The force per unit area on a surface

  15. Pressure is caused by gas particles slamming into the container’s walls.

  16. Units of Pressure: 1) atmosphere (atm) 2) kilopascal (kPa) 3) millimeters of Mercury (mm Hg) 4) Torr 5) Pounds per square inch (lb/in2) 1 atm = 101.3 kPa = 760 mm Hg = 760 torr = 14.7 lb/in2

  17. STOP…collaborate and listen

  18. Boyle’s Law P1V1 = P2V2 1 = before 2 = after MUST BE AT CONSTANT TEMPERATURE!!

  19. A gas occupies a volume of 0.458 L at a pressure of 1.01 kPa and temperature of 295 Kelvin. Although the temperature stays the same, the volume is increased to 0.477 L. What is the new pressure? 0.970 kPa

  20. Charles’ Law V1T2 = V2T1 1 = before 2 = after MUST BE AT CONSTANT PRESSURE!!

  21. What will be the volume of a gas sample at 309 K if its volume at 215 K is 3.42 L? Assume that pressure is constant. 4.92 L

  22. Gay-Lussac’s Law 1 = before 2 = after MUST BE AT CONSTANT VOLUME!!

  23. A balloon with a pressure of 0.900 atm is heated from 105 K to 155 K. If volume is held constant, what is the new pressure? 1.33 atm

  24. Confused yet???There’s aneasier way…

  25. Combined Gas Law 1 = before 2 = after JUST HOLD ONE QUANTITY CONSTANT!! (take it out of the equation)

  26. The gas in a 0.010 L container has a pressure of 1.39 atmospheres. When the gas is transferred to a 0.017 L container at the same temperature, what is the pressure of the gas? 0.82 atm

  27. The gas inside a 70.8 mL piston has a temperature of 35.0°C. If the temperature is raised to 100.0°C, what is the new volume of the gas? 85.7 mL

  28. An elastic container is inflated to a volume of 18.0 liters at a pressure of 1.26 atm. The container then expands to a new volume at a pressure of 1.05 atm. What is the new volume? 21.6 liters

  29. Avagadro’s Law Equal volumes of gas (at same P and T) contain the same amount of particles

  30. 1 mole = 6.02 x 1023 particles 1 mole = 22.4 L Only works at same P and T

  31. Ideal Gas Law The mother of all gas laws. It includes everything! PV = nRT

  32. PV = nRT P = pressure (atm) V = volume (L) n = moles (mol) R = Gas Constant T = Temperature (Kelvin)

  33. PV = nRT MUST USE THESE UNITS!!!

  34. If the pressure exerted by a gas at 0.00°C in a volume of 0.0010 L is 5.00 atm, how many moles of gas are present? 2.2 x 10-4 moles

  35. Ideal gases don’t really exist… …real gases do!

  36. Real Gas All gases are real gases. DUH!!

  37. Ideal Gas A gas that is described by the KMT postulates.

  38. Ideal Gas Law works most of the time.

  39. It does NOT work at very low temperatures and very high pressures.

  40. Dalton’s Law of Partial Pressures The sum of the partial pressures of the gases is equal to the total pressure

  41. Dalton’s Law of Partial Pressures Ptotal = P1 + P2 + P3 + …

  42. A balloon contains O2 and N2 gas. If the partial pressure of the O2 is 0.75 atm and the partial pressure of the N2 is 0.55 atm, what is the total pressure of the balloon? 1.30 atm

  43. The gas inside a 70.8 mL can contains H2O(g) and CO2(g) and has a total pressure of 760 mm Hg. If the partial pressure of the H2O is 350 mm Hg, what is the partial pressure of the CO2? 410 mm Hg

  44. Graham’s Law Gases with smallermasses move faster than gases with large masses (like a kid in Walmart)

  45. H2 moves faster than N2. Which of the following gases moves the fastest? O2 CO2 NH3 Cl2 I2 H2O Ar N2 Br2

  46. STP Standard Temperature and Pressure: 0°C and 1 atm

  47. How many moles of N2 gas are in a 4.5 L balloon at STP? 0.20 moles

  48. A gas at STP is heated to 55°C. What is the new pressure if volume is held constant? 1.2 atm

  49. A gas tank contains CO2 and O2 gas. What is the total pressure in the tank if the partial pressure of CO2 is 0.45 atm and the partial pressure of O2 is 0.55? 1.00 atm

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